Little用作副词修饰动词且放在句首时，后面的句子要用倒装句式。如：

Little do they know about her alternative career. 他们对她的另一个职业一无所知。

Little did they know that the truth would be discovered. 他们一点也不知道实情会被发现。

我的疑问是，这样的用法一定要用于倒装句吗？它也可以用于不倒装的句子吗？

同意cgh007老师解答

(1)little只有当作否定副词放在句首时候，才倒装，其他情况可以不用倒装

A（数量上）微少的，少到几乎没有的（可用so，too，very修饰）

I had little money and little free time.  

我没什么钱，也没多少空闲时间。

I find that I need very little sleep these days.

我发现最近我只需要睡很少时间。

B:（频率或程度）微小地，小到几乎没有地

On their way back to Marseille they spoke very little. 

返回马赛的路上，他们没怎么说话。

Only Africa is at present little affected by hard drugs.  

目前只有非洲没怎么受到硬毒品的影响。

C:（数量上）不多的（亦作a very little）

 Mrs Caan needs a little help getting her groceries home.

卡安太太需要有人帮把手将食品杂货拿回家。

A little food would do us all some good...  

吃点东西，对我们大家都会有好处。

D:短时间地；一会儿地

He walked a little by himself in the garden.  

他一个人在花园里散了一会儿步。

E:（程度上）一点地，少量地

He complained a little of a nagging pain between his shoulder blades.

他有几句提到说肩胛骨之间一直在疼。

He was a little bit afraid of his father's reaction...  

他有点害怕父亲的反应。

F: 逐渐地；一点一点地

In the beginning he had felt well, but little by little he was becoming weaker.

 一开始他感觉很好，但慢慢地就变虚弱了。

I would have to learn, little by little, to exist alone.  

我得慢慢学会独自生活。

(2)little 形容词用法时不倒装

A:小的（比small略欠正式）

 We sat around a little table, eating and drinking wine. 

我们围坐在一张小桌旁吃吃喝喝。

the little group of art students.  

那一小群艺术专业的学生

B:娇小的；小巧的

 She's got the nicest little house not far from the library.  

她有一幢非常漂亮的小房子，就在离图书馆不远处。

a little old lady. 

身材娇小的老太太

C: 幼小的

 I have a little boy of 8.

我有一个8岁的小男孩。

When I was little I was very hyperactive.  

我小时候异常好动。