In the equivalent device of dynamic test and launch control system of new generation launch vehicle, tens of 4 to 20 mA current sources are used to simulate air pressure transmitter of distributing device. This proposes higher requirements to output precision, integration degree,reliability and so on. This paper proposes a method which uses dsPIC digital signal controller to control PWM output and low-pass filter to achieve D/Aconverter,finally two-wire 4 to 20mA current output is realized. In this paper, the design theoretical foundation as well as hardware and software realization are analyzed. This scheme has advantages of advanced technology, high output accuracy, reliability, high integration,less peripheral circuits, simple software control, ect. It has been successfully applied in equivalent device of CZ-6 new generation launch vehicle dynamic test and launch control system.