A sinusoidal signal generator with controllable frequency and phase is designed and realized by using direct digital frequency synthesis technology. After the clock frequency is given, the frequency of the output signal depends on the frequency control number, the frequency resolution depends on the accumulator bits, the phase resolution depends on the address line bits of ROM, and the amplitude quantization depends on the data bit word length of ROM and the bits of D / a converter. The computer digital system controls its output power, amplitude and energy by setting its frequency, tracking compensation, amplitude setting, amplification and matching output and signal detection and analysis. A variety of application modes such as time, energy, distance dimension and depth dimension are set in the ultrasonic computer-controlled welding system to meet different welding requirements. The system has the characteristics of high precision, intuitive display, high degree of intelligence, flexible control, good performance, better reliability and stability, convenient use and high performance price ratio.