No sooner had I reached home than it began to rain.

Hardly had I reached home when it began to rain.

这两句话主句的过去完成时可不可以改为一般过去式？

我知道“hardly +过去完成式 when+一般过去”和“no sooner+过去完成式 than+一般过去时”是固定用法，但是觉得也可以都用一般过去式。因为had done是强调“过去的过去”，而有了no sooner, hardly 后，没必要去强调先后顺序，所以从语法上说也没问题啊!

解答如下：

主句必须使用过去完成时态，不可以使用一般过去式。

I had no sooner reached home than it began to rain

No sooner had I reached home than it began to rain.

I had hardly reached home when it began to rain

Hardly had I reached home when it began to rain.

主句在从句动作之前完成。