数学成绩好用英文怎么说

"good in math" 或 "good at math" 可以用来表示数学成绩好。

来源：这是一种常用的习语，表达的是对某一学科的技能或能力的评价。

例句：

He is good in math, so he got an A in his math test.
(他数学成绩很好，所以他数学考试得了A。)
She is good at math, so she decided to major in mathematics in college.
(她数学成绩很好，所以她决定在大学里学数学专业。)