Laser technology is the key technology in laser ranging system. In the application of high performance ranging, the requirements of laser include high peak power and good stability. In order to achieve far away laser ranging， a large current and high stability driving circuit for pulse laser was designed. The mathematical model of the circuit was established, and the influence of the key parameters on the pulse constant current source was analyzed by using Matlab simulation software. The simulation results show that the voltage swing rate of the open-loop operational amplifier, the time constant of the later stage circuit and the circuit noise have an effect on the average value of the output current, the rise time and the stability. Finally, the test results show that the circuit module can generate 20 A pulse constant current, the stability is about 99%, and it can drive the pulse laser to work, which meets the requirements of ranging system.