前面用at比较多，有时也可以用 in，区别如下：

• at the beginning of：在…开始时 （表示一个时间点，通常与发生一次行为搭配使用）
• in the beginning of：在…开始期间（表示时间段，通常与多次行为搭配使用）

例句：

• Tom retired at the beginning of this year.
• In the beginning of the match, Tom gave us a lot of trouble.

看下面的对比：

• At the beginning of the term, the headmaster addressed us in a speech.
• In the beginning of the term, several lectures will be given by some professors.