Abstract: Relay protection has been greatly promoted by its testing technique. The concept based on the embedded industrial control computer results in many problems of the traditional relay protection testing device, such as high cost, big system and so on. According to the concept “Simulation algorithm and outputting data operates separately”, the design of new relay protection testing equipment is proposed based on “PC+DSP board”. The equipment firmware procedure of the hardware platform and the application of the USB Device Driver through CCS2.0 and VC++6.0 tools are developed. The standard sine wave is employed as the example. The testing system shows fine performance.