This paper studied the design and implementation of large pulse constant current source system required by engine ignition. The system used PID control algorithm, through power semiconductor devices to achieve pulse constant current. The pulse constant current system achieve rise time less than 200us, pulse width between 50ms ~ 150ms adjustable, continuously 0A ~ 12A adjustable current, can be connected to 0.5Ω ~ 4Ω small load. Conventional constant current system often can’t get to 12A current, or the current is not continuously adjustable, or the current rise time can’t meet the requirements, or the load is too large, all above can’t meet the system requirements of engine ignition. Compared with the traditional constant-current source system, this system has short rise time, pulse width adjustable, current continuously adjustable, small load, reliable, controllable, simple structure and so on.