be busy doing sth 是英语中的常用句式。如：
They were busy getting the harvest in. 他们正忙着收成。
The women were busy preparing the wedding feast. 女性们正忙着筹备结婚宴会。
They were busy laying the drains for the new houses. 他们正忙着给新房铺设下水道。
请问假如要在 doing sth 前面加一个介词，是 in 还是 with？凭感觉仿佛 be busy in doing sth 和 be busy with doing sth 都非常顺口。
依据英语惯使用方法，busy doing sth. , busy with doing sth. 和 busy in doing sth. 都是正确的。请看下面的实例：
1. Two of them were busy making artificial flowers. 他们之中有两个人忙着做假花。
2. We are busy preparing for the examination. 大家正忙着筹备考试。（《英语惯使用方法大词典》）
3. Im busy getting the house redecorated. 我正忙着重新装饰房子。
（以上内容摘自赵振才教授编著的《英语容易见到问题解答大词典》增订版）
