Polytetrafluoroethylene (PTFE) is widely used in the field of antifriction materials, but its poor wear resistance limits its application. Nanomaterial modification is an effective method to improve the wear resistance of PTFE. Silicon nitride (Si3N4) has high strength and low-friction-coefficient properties, which can overcome the poor wear resistance of PTFE. With modified Si3N4 and PTFE as raw materials and polyamideimide (PAI) as binder, the PTFE/Si3N4 composite coating is prepared by spraying-curing method, and the tribological properties of the coating are investigated. The structure of Si3N4 nanoparticles before and after modification is characterized using scanning electron microscope (SEM) and fourier transform infrared spectroscopy (FT-IR). In addition, the hardness and tribological behavior of the coating are also studied by microhardness tester and friction and wear tester. The results show that KH-570 has been successfully grafted on the surface of Si3N4 nanoparticles, and the surface of modified Si3N4 nanoparticles becomes rougher, which is benefit for the dispersion of Si3N4 nanoparticles. Besides, Si3N4 nanoparticles can improve the hardness and tribological properties of the PTFE composite coating. When the mass fraction of modified Si3N4 nanoparticles is 1%, the coating achieves the highest hardness (11.1HV) among the samples. And the friction coefficient and wear rate are 0.0755 and 3.78×10-3 m3·N-1·m-1 respectively, which is the lowest friction coefficient and wear rate among the samples. At this time, the wear mechanism of the coating is mainly abrasive wear. However, when too much modified Si3N4 nanoparticles is added, the serious agglomeration occurs, which will reduce the tribological properties of the coating.