Will affect. Returning to China to write a thesis will affect the certification of studying abroad. Some countries or schools will require the completion of thesis defense after returning to China before issuing the certificate of studying abroad. A certificate of studying abroad refers to a document that can prove your academic qualifications and academic achievements before studying abroad. It is an important basis for judging whether you have the qualification to study abroad. Under normal circumstances, the relevant institutions will require applicants to submit documents to prove that their study abroad activities are legal.