Abstract: In order to improve testing precision of frequency response of actuators,systematic error produced by the testing system is analyzed with the phase error caused by A/D multiplex sampling discussed specially.Based on error analysis,a method of correction is advanced which can amend the amplitude and phase frequency characteristics using the frequency response data of the testing system.Experimental results showed that the testing system can cause phase delay and amplitude decay of testing signals and the systematic error can be corrected effectively by testing the frequency response of the testing system.