Abstract: A test device for flack flowing systems based on virtual instrument technology is developed.Test signals such as the step signal,constant speed signal,sinusoidal signal are generated by a digital sine machine.High-speed,high-precision test of the error,velocity,current,and shooting signals are accomplished by computer,realizing the functions such as test result calculation and shooting error test.In order to get smooth velocity when the flowing system started or stopped,the paper adopts the guide function method in the output control of the sine machine.The results of practical application proved that it is an accurate system with an accuracy of 0.006° in its position error signals.