Cold spraying is a kind of low-temperature solid-state coating process in which spraying particles undergo extensive plastic deformation at extremely high strain-rates. As a result, cold sprayed coatings have excellent mechanical, electrical and thermal properties. Due to the large hardness difference between copper and stainless steel, it is difficult to prepare copper coating on stainless steel. Therefore, the work aims to prepare copper coatings with high interfacial bonding strength on thin 304 stainless steel substrates by optimizing the cold spraying process, and to study the effect of heat treatment process on the microstructure and properties of cold sprayed copper coatings. The 304 stainless steel plate was cut into 100 mm × 100 mm × 1 mm by wire cutting, and the base material was polished and cleaned. With high-purity nitrogen and helium as accelerating gases, copper coating was prepared on the surface of 1 mm thick 304 stainless steel substrate by cold spraying. Optical microscope (OM) was used to characterize the porosity and microstructure of the coating. The tensile cross-sectional structure of the coating was analyzed by field emission scanning electron microscopy (FESEM). The deposition appearance of single particle on the surface of stainless steel was observed by changing the powder feeding speed. Vickers microhardness tester, universal tensile testing machine and eddy current conductivity tester were used to test and analyze the effect of annealing heat treatment on hardness, bond strength and electrical conductivity of cold sprayed copper coating on the surface of 304 stainless steel substrate. It was difficult to obtain a copper coating on the 304 stainless steel substrate with nitrogen as the accelerating gas, and the coating peeled off during deposition and failed to form effective bonding. With helium as the accelerating gas, a high-density copper coating with a bonding strength higher than 81.7 MPa, a hardness of 99.6HV0.1, and a porosity of less than 0.1% could be successfully obtained on the surface of the 304 stainless steel plate. Compared with nitrogen, helium used as the accelerating gas caused a larger plastic deformation of the 304 stainless steel substrate by the accelerated particles. The recrystallization caused by annealing heat treatment could significantly eliminate the effect of work hardening during the cold spraying process. As the heat treatment temperature increased from 300 ℃ to 500 ℃, the coating hardness decreased from 99.6HV0.1 to 63.74HV0.1. When the annealing temperature was 400 ℃, the conductivity of the coating was the best (93.94% IACS). When the heat treatment temperature increased to 500 ℃, the conductivity of the coating decreased abnormally (89.02% IACS). By analyzing the microstructure of the coating, the high heat treatment temperature caused the diffusion and segregation of oxygen inside the coating and resulted in the increase of the defects and the decrease of electrical conductivity. Compared with nitrogen, the helium can be used as the accelerating gas to prepare a coating with high density and high bonding strength on thin stainless steel substrate. Annealing heat treatment has a great effect on the hardness and electrical conductivity of the copper coating, and the conductivity of the coating after annealing heat treatment can reach a level comparable to that of as-cast copper.