他做花木生意。
× He deals with flowers.
√ He deals in flowers.
解析：
deal with和deal in均为短语动词，与买卖有关，但deal with主要指“与……进行交易”[do business, esp trade with]；而deal in却表示“经营”[trade in]。
举例：
1. Do you deal with Smith, the butcher?
你与肉商史密斯有生意来往吗？
2. We've dealt with the same firm for years and can thoroughly recommend it to you.
我们与同一家公司做了多年买卖，完全可以将它推荐给你们。
3. This shop deals in woolen goods.
这家商店经营毛纺织品。
4. This gallery deals in 19th century paintings.
这家画廊经营19世纪的油画。