他在干什么用英语怎么说

"What is he doing?"

This phrase can be translated into English as "What is he doing?" It is a simple and direct question that inquires about the current activity of someone. The sentence structure is subject-verb-object, where "he" is the subject, "is" is the verb, and "doing" is the object. This question can be used in various contexts to seek information about someone's actions or intentions.