The invention discloses a nano-grade structure light diffraction device based on random laser speckles. The width of a diffraction unit of the light diffraction device with the structure is only nanometers, even dozens of nanometers; and the nano-grade structure light diffraction device has the advantages of high resolution ratio, high contrast ratio, large view field angle and the like. On the basis, the invention further provides a manufacturing method of the nano-grade structure light diffraction device, namely a phase light field interference photoresist process. The high-quality light diffraction device with a depth perception structure can be prepared by utilizing the method. Compared with a traditional optical element machining technology, the phase light field interference photoresist process provided by the invention has the advantages of high resolution ratio, high phase matching precision and the like; and compared with photoetching technologies including ultraviolet projection exposure, electron beam direct writing and the like, the photoetching technology provided by the invention has the advantages of high speed, low cost and the like.