询问对方大学专业的英语表达有以下几种：
What's your major？
What are you majoring in？
Could you please tell me your major？
Would you mind telling me your major？
What do you study in the university？
Which college/school are you in？
What is your main course？
这些表达方式在日常交流中都可以使用，具体选择哪种表达可以根据语境和对方的熟悉程度来决定。例如，如果对方和你关系较为熟悉，可以直接问“What's your major？”；如果对方是第一次见面或者你想表现得更为礼貌，可以使用“Could you please tell me your major？”或“Would you mind telling me your major？”。