这个问题虽然有些进展，但仍然困扰了很久，就目前很多对这个问题的研究都不是那么令人满意，故开辟一个知识专项，以供大家交流。

1. 赵振才教授是我喜欢的学者之一，可惜去世得早。在其著作中只提到用 in the playground和 at the playground 都是正确的，前者侧重空间，后者侧重地点。At 侧重表示某个点这在Close的著作中已有阐述。赵教授就没提 on the playground 是怎么回事，遗憾！

2. 葛老的惯用法一书中确实提到：in the playground 经常见到，而 on the playground 用的很少。

3.在小日本编写的英美惯用法词典中，同样提到 on the playground 不常用，而 in the playground 很常用。

目前我能找到的关于此的讨论就仅是以上三个描述。既然前人没有能为我们解惑，或者说寻找已经存在的答案几乎不可能的时候，我们需要自己摸索，能站在巨人的肩膀上探索仍然比瞎撞还是容易得多，这是我从具有高超语言能力的 Erades 上学到的一点思想皮毛。我想从具体实例来分析这其中是怎么回事：（以下例句素材均来源于权威词典和原版书籍）

…ancillaries who look after the children in the playground

Children scampered off the yellow school busand into the playground.

He staggered around the playground, screaming in agony.

There was a sandpit, a seesaw and a swing in the playground.

We shot up heroin in the playground.

The children were running about in the playground.

She pushed me over in the playground.

The little children rode their tricycles around the playground.

A group of girls were bullying [picking on] her at the playground.

I released my son’s hand, and he ran out onto the playground.

Sam pushed me over in the playground.

The girls were skipping in the playground.

I'm afraid your son had a slight mishap in the playground.

The kids outran the teacher to the playground.

As soon as the bell rang the children spilled into the playground.

a kite flying above the playground.

There were children fighting in the playground.

Local parents were the moving force/spirit behind the safety improvements at the playground.

The other children used to taunt him in the playground because he was fat and wore glasses.

The children ran in zigzags around the playground until they were exhausted.

He was cornered in the playground one day by the school bully.

She's one of the ancillaries who look after the children in the playground.

The children were having races in the playground.

Two boys were having a fight in the playground.

The children spent a happy hour at the playground on the swings and climbing frame.

'What do you know?' he said, as if I was new on the playground.(不是我们讨论的，是比喻的意义)

They look at the boys scrapping in the playground.

Visualize yourself in the playground of your elementary school.

kids in the playground screaming with laughter

Mr Morris benched me for taking food into the playground.

He bullies all the other little boys in the playground.

The children charged into the playground.

children dashing harum-scarum around the playground

The boys were monkeying about in the playground , and one of them got hurt.

The children were beginning to straggle in from the playground.

Children should not be left unattended in the playground.

A large number of children were running around in the playground.

Billy ran over to the playground.

Ashley was put on the playground duty.(不是我们讨论的, put on短语)

If you run about in the playground you will soon get warm.

Scraps in the playground are a pretty frequent occurrence.

Children were scampering and wrestling in the playground.

Some others were standing about in the playground.

When the bell rang, the children poured into the playground and ran in all directions.

Expecting teachers to mind children in the playground is an unfair imposition on them.

The children who are playing in the playground live down the street.

Boys will be boys and it’s normal for there to be some fighting in the playground.

A swarm of children ran into the playground.

There was a struggle between the two boys in the playground.

A teacher caught them smoking in the playground.

Some of the students regularly try to pick fights in the playground.

The children quickly lined up in the playground.

The girls walked across the street to the playground.

She ran toward the playground to see her friends.

The two boys took part in a set-to in the playground.

Kids were dashing across the playground chasing a ball.（固定搭配）

It's your turn to supervise the children in the playground.

When school was over, all the boys in the class emptied out into the playground.

以上是各种表达方法的例证，其中以用 in the playground 确实极为常见，这与大咖们的说法比较一致，至于用 into, to, at, about, toward 或是 around 和 across 等这些有的是强调空间，有的是强调地点，有的强调方位，有的是固定搭配，比较正常。

用 on the playground 还是有的，只是比较少，大多出现在美语的词典书（韦氏高阶和Random House Websters Dictionary of American English）上：

The children run out and play on the playground at recess.

Children scuffled on the playground.

The children were cavorting on the playground.

They tussled on the playground.

只有这几例。

总结：简单说 in 强调空间，on 强调平面，playground 一般指学校操场，用 in 的原因是学校操场一般都是围起来的，把它看成了一个三维空间。而一般说 on the floor 是把 floor 看成了平面。

再看下面的例句：

run through a playground

Children ran through the playground as their mothers looked on.

按照上面的解释，用 through 是合理的，因为 through 强调空间（across 强调平面）。

只能说，这种解释指针对大部分情况。用 on the playground 确实少的可怜，但毕竟还是有的，只能认为美语会用 on the playground.