1. First of all, you need to report to the local public security bureau or police station and explain that your diploma is lost. Report proof will be provided for subsequent use.

2. Secondly, with the registration certificate and other materials, you can contact the Academic Affairs Office or Department of Nanjing University of Aeronautics and Astronautics to consult the specific process and required materials for the replacement of the diploma. You need to provide identification, school registration certificate, registration card and other documents.

3. Then according to the regulations of the school, you need to pay a certain replacement fee. Specific fees and payment methods can be consulted with the school department.

4. Finally, according to the requirements of the school, submit the required materials, fill in the corresponding forms, and wait for the school to verify and go through the formalities. This process needs some time, wait patiently.