The invention provides an electromagnetic and pressurization piezoelectric combined fuel gas injection device. The electromagnetic and pressurization piezoelectric combined fuel gas injection device is formed by combining a fuel gas pressurization device, an electromagnetic control device, a piezoelectric control device and two fuel gas nozzles, wherein a fuel gas pressurized by the pressurization device is charged into the fuel gas nozzle controlled by the piezoelectric control device, the unpressurized fuel gas is charged into the fuel gas nozzle controlled by the electromagnetic control device, pressure of the fuel gas injected into a combustion chamber can be changed in a single cycle of an engine, thus a mixing degree of the fuel gas and air is changed, the combustion characteristic of the fuel gas is flexible and changeable, and the changeability requirement of the injection pressure in the single cycle of the engine is met; pressurization for the fuel gas is controlled by a pressurization electromagnetic valve, and switchover between pressurized injection for the fuel gas and unpressurized injection for the fuel gas can be rapidly realized; injection for two paths of the fuel gas is controlled by the electromagnetic valve and a piezoelectric component respectively, and switchover between injection of the single fuel gas nozzle and injection of the double fuel gas nozzles can be rapidly realized; and the fuel gas is sealed by fuel oil, and avoidance for leakage of the fuel gas through a needle valve partner is facilitated, and thus the dynamic property of the engine and the economical efficiency of fuel are improved.