The invention aims at providing a combined electromagnetic fuel oil injection and pressurizing piezoelectric fuel gas injection mixed fuel injection device.The mixed fuel injection device comprises a fuel gas pressuring part, an electromagnetic and piezoelectric control part, a nozzle part, a fuel gas inlet channel, a fuel oil inlet channel and the like.A pressuring electromagnetic valve is utilized for controlling motion of a pressuring piston to achieve fuel gas pressurization, an electromagnetic valve is utilized for controlling a fuel oil nozzle to achieve fuel oil injection, a piezoelectric element is utilized for controlling a fuel gas nozzle to achieve fuel gas injection, and three working modes of pure fuel oil injection, fuel oil and non-pressurized fuel gas dual-fuel injection and fuel oil and pressurized fuel gas dual-fuel injection can be achieved.Switching of fuel gas pressurizing injection and fuel gas non-pressurizing injection can be rapidly achieved, the different requirements of different powers of a dual-fuel engine on fuel gas injection pressure are met, switching of pure fuel oil injection and dual-fuel injection can be achieved, the fuel oil injection amount and fuel injection timing are controllable, and therefore the gas injection pressure and injection speed are increased, and the power property of the engine and the fuel economical efficiency are improved.