This paper devisers aShigh precision digitally controlled constant current source. This system, including integrated operational amplifier LF356 with deep negative feedback, is based on DSP. PID control applied to the constant-current power supply. System may adjust the output current in real time. The button presetting, step, displaying the given value and actual measuring value with LCD make our system’ functions. The test results indicate that this system has the advantages of reliability and high-precision output. In the occasions with high power supply, it has a potential value for application.