The invention discloses a mixed shot blasting method which specifically comprises the following steps: respectively placing shots in one or more specifications into 21, 22 to 2i (i is greater than or equal to n) cabins of an auxiliary cabin; sequentially opening one or more of the 21, 22 to 2i (i is greater than or equal to n) cabins of the auxiliary cabin or opening a plurality of corresponding valves at the same time; proportioning the shots according to requirement, and after shots in one or more specifications enter into a main cabin, fully mixing the shots in the main cabin; opening a valve which connects the main cabin and a shot blasting mechanical arm pipeline, wherein a shot blasting mechanical arm blasts shots to a workpiece; after stopping blasting shots, enabling the shot blasting mechanical arm to return to an automatic nozzle-changing cabin of the shot blasting mechanical arm for replacing the nozzle, wherein the rest shots in the main cabin enter into a shot recovery device. The method disclosed by the invention eliminates the risk of micro-cracks generated by same blast shots, so that multiple functions of the device are realized, the work efficiency is improved and the labor intensity is reduced.