An azimuth-drive motor system structure of a heavy load inertially stabilized platform comprises an azimuth-drive motor body structure, a motor measuring structure and a motor locking mechanism. The azimuth-drive motor body structure comprises a motor stator and a motor rotor. The motor measuring structure comprises a grating measuring ruler structure and a grating read head structure. The motor locking mechanism comprises a motor locking spring and a motor locking pin. The azimuth-drive motor body structure realizes control of azimuth direction freedom degree, and realizes isolation of airplane azimuth direction angle motions according to control instructions. The motor measuring structure finishes angle information measurement of azimuth direction relative rotary angles, and feeds back to a processor to complete accurate control of azimuth direction. The motor locking mechanism realizes static state of the heavy load inertially stabilized platform, and guarantees fixed azimuth pose during aerial photography and absolute static during non-working state.