两者的区别有点复杂，下面仅谈谈几条基本用法：

▲long ago 和long before都可表示“很久以前”，long ago通常与一般过去时连用。如：

it was abandoned long ago. 它很久以前就不用了。

Long ago, pirates carried daggers. 很久以前海盗随身携带匕首。

而long before，则多用于过去完成时，表示比过去某时早得多的时间。如：

She said she had seen the film long before. 她说她很久以前就看过这部电影。

That had happened long before (ie a long time earlier). 那事老早就发生了（比过去某时早得多）。

▲除以上用法外，long before 中的 before 还可能是介词（后接宾语，用于引出介词短语）或连词（后接句子，用于引导时间状语从句）。如：

Trains were invented long before cars.  火车远比汽车发明得早。

The champagne gave out long before the end of the reception. 在招待会结束前很久，香槟酒就都喝完了。

The photograph in question was taken long before I met you. 提到的那张照片是在我遇见你很久之前拍的。

We used to live in Paris, but that was long before you were born. 我们曾住在巴黎，但那是你出生前很久的事了。