The invention discloses an all-optical deep diffraction neural network system and method based on spatial partially coherent light. The all-optical deep diffraction neural network system comprises a conversion module which is used for converting an inputted spatial partially coherent light signal into a coherent light signal, an all-optical deep diffraction neural network module which is used forconverting, extracting and compressing coherent optical signals, and an information acquisition module which is used for receiving the output signal of the all-optical deep diffraction neural networkmodule and generating a processing result of the spatial partially coherent optical signal according to the output signal. According to the all-optical deep diffraction neural network system, the application field of the all-optical deep diffraction neural network can be expanded, so that the all-optical deep diffraction neural network can better complete more complex machine learning tasks, and particularly can complete natural scene image recognition processing and calculation tasks.