do well in：在……某方面干得好；做得好；擅长
be good at：善于；擅长；擅长于；在某方面擅长
二者的区别：
Ⅰ. be good at / in 意思接近于 do well in. “在（某方面）出色；擅长……”.be good at / in 强调一种笼统情况,而do well in 可表示一种情况,也可指在具体的一次活动中表现出色.
be good at 的反义词组为：be poor (weak) at (in). do well in 的反义词组为：do badly in. 如：
① Mary is good at / in maths. = Mary does well in maths. 玛丽数学很好（指情况）.= 玛丽数学学得很好.
② Tom did well in (不宜用be good at.指具体一次)that English test / sports meeting.汤姆在那次英语考试中（运动会中）考得很好（表现出色）.
③ Wu Dong does badly in his lessons. = Wu Dong is weak / poor / at / in his lessons.吴冬功课不好.（指情况）
④ Mei Ying did badly in the high jump 梅英在跳高比赛中成绩不好.（具体一次,不宜替换.）
⑤ Mei Ying is weak / poor in / at high jump.梅英不善于跳高.（指笼统情况）
Ⅱ. do well 和do badly可单独使用,表一种情况；而be good / weak / poor 一定要借助于介词in 或at, 强调在某一个方面,才能表达一个完整的意思.如：
He does well / badly at school. 他在学校里功课很好/很差.
good和well都表示“好”,区别在于：
（1）good作形容词,常用来指人的品行好,或事物的质地好,也常用来向别人问好.
a. Miss Gao is a good teacher. （人好）
b. Your picture is very good. （物好）
c. Good morning. （问好）
（2）well 做形容词时,指人的身体好,健康的
a. —How is your father? —He’s very well.
well 常做副词,修饰动词用.
b. He speaks English well.
best是good 和well的最高级形式.如：I think John's plan is best.
我认为约翰的方案最好.
