The invention relates to a gas supply device used for magnetron sputtering and adopting gas as a doping source. The gas supply device comprises a gas supply ring (1), a group of gas outlets (3) is evenly distributed in the inner wall (2) of the gas supply ring (1), and an annular cavity is formed in the gas supply ring (1). Each gas outlet (3) communicates with the annular cavity, a gas inlet pipe(4) is further connected to the gas supply ring (1) and connected with the annular cavity, and a lifting lug (5) is further connected to the gas supply ring (1). The gas supply device has the advantages that the device overcomes the defects that in an existing gas supply system, gas distribution is not uniform, the ionization degree is low, the doping amount cannot reach a target value, and quantitative analysis cannot be carried out; the doping gas source can be effectively promoted to be ionized, the utilization rate of the gas is improved, the doping amount is increased, and the purpose ofeffectively conducting doping to finish coating is achieved; and meanwhile, the quantitative analysis can be performed accurately, and a better accurate scheme is provided for further research and development of multi-element doped magnetron sputtering.