After Diploma in EEE, can I join B.Tech aerospace engineering?

Yes, you can. But, the criteria usually varies from university to university. So, visit official website or call the admission counselor in which you are seeking admission to have detailed information regarding the same. The top colleges are: Jawaharlal Nehru Centre for Advanced Scientific Research

Dear Ranjit! After Diploma in EEE, yes you may get admission in B.Tech Aerospace Engineering. But that would be better if you directly set up the contact with the concerned university. Because after all its depends upon the college discretion itself. Hope this helps. Good Luck.