The authors introduce the requirement of exciting signal for ultrasonic motor testing,research on direct digital frequency synthesis(DDFS) technology basing on personal computer.According to the requirement of ultrasonic motor testing,DDFS is realized for sine wave and periodic chirp signal basing on personal computer.The output signal is(tested) and analyzed.DDFS basing on personal computer,convenient to utilize the software and hardware resources,is fit to application in the test system.