The invention aims at providing a pressurized leakage-free electromagnetically-controlled gas injection device. The pressurized leakage-free electromagnetically-controlled gas injection device comprises a pressurization part, a control part, a nozzle part and an injection device shell. A pressure is formed in a control cavity by virtue of high-pressure oil to lift a needle valve, response is rapid, and control for a gas injection amount is accurate; a control oil drainage path passes through the upper parts of electromagnetic valves to play a cooling role, thus the stability of the working of the electromagnetic valves is improved; a gas is pressurized by virtue of a pressurization piston, the processes of gas pressurization and gas injection are controlled separately by virtue of two electromagnetic valves, the gas injection process can be flexibly switched between a pressurization mode and a non-pressurization mode, and the pressurization process is slow at first and then fast, thus a variable gas injection rule can be realized, and the requirements of different working conditions of an engine on a gas injection pressure can be met; and in the pressurization part, gas leakage of a pressurization chamber is prevented by virtue of a long sealing coupling and a large oil cavity, a sealing ring belt is arranged between the needle valve and a needle valve base, and a part of control oil is introduced as sealing oil for sealing the gas, thus gas leakage in a needle valve cavity is prevented.