Ⅰ. be good at / in意思接近于do well in. “在(某方面)出色;擅長……”。be good at / in強(qiáng)調(diào)一種籠統(tǒng)情況，而do well in可表示一種情況，也可指在具體的一次活動(dòng)中表現(xiàn)出色。

　　be good at的反義詞組為：be poor (weak) at (in). do well in的反義詞組為：do badly in. 如：

　�、� Mary is good at / in maths. = Mary does well in maths. 瑪麗數(shù)學(xué)很好(指情況)。= 瑪麗數(shù)學(xué)學(xué)得很好。

　　② Tom did well in (不宜用be good at.指具體一次)that English test / sports meeting.湯姆在那次英語考試中(運(yùn)動(dòng)會(huì)中)考得很好(表現(xiàn)出色)。

　�、� Wu Dong does badly in his lessons. = Wu Dong is weak / poor / at / in his lessons.吳冬功課不好。(指情況)

　　④ Mei Ying did badly in the high jump.梅英在跳高比賽中成績不好。(具體一次，不宜替換。)

　�、� Mei Ying is weak / poor in / at high jump.梅英不善于跳高。(指籠統(tǒng)情況)

　　Ⅱ. do well 和do badly可單獨(dú)使用，表一種情況;而be good / weak / poor 一定要借助于介詞in 或at，強(qiáng)調(diào)在某一個(gè)方面，才能表達(dá)一個(gè)完整的意思。如：

　　He does well / badly at school. 他在學(xué)校里功課很好/很差。