To remember seeing him dance in Engpsh, you can say "I remember watching him dance." This phrase comes from the verb "to remember," which means to retain information or a memory in one's mind, and the verb "to watch," which means to look at something for a period of time, usually with attention and interest. Here are some examples with Chinese translations:

I remember watching him dance at the party last night. (我记得昨晚在聚会上看他跳舞。)
Do you remember watching him perform on stage? (你还记得看他在舞台上表演吗？)
I'll never forget watching him dance with such grace and skill. (我永远都不会忘记看他跳舞时那么优美和熟练。)