Base on direct digital frequency synthesis (DDS), the paper introduces working principle and composition of the dual program design technology of high precision signal generator. Using STC12C5A60S2 to control the two pieces of DDS, the paper realizes the output sine wave, triangle wave and dual square wave. Dual signal frequency can be continuously adjustable in the range of 1 Hz~2 MHz and the resolution is less than 1 Hz, the phase difference regulating range is 0°~359° and phase difference resolution is less than 0.1°. Through the matrix keyboard, it can facilitate the realization setting of frequency and phase difference. Using oscilloscope, it can be seen that the output waveform is stable and the output of phase difference is accurate. The system has the characteristics of simple structure and convenient operation.