The paper presents the digital phase measuring instrument based on MSP430 single-chip microcomputer. The instrument adopted the technology of DDS to generate sinusoidal signal, and FPGA to achieve phase difference measurement and polarity judgment. The system is composed of a filtering circuit, a phase shifting network, a shaping circuit, matrix keyboard, LCD display module and the frequency is in the range from 200Hz to 10kHz, the phase difference is in the range of-180°~+180 °, the resolution ratio is 0.1°, the absolute error is less than ±2 °, and the relative error is less than ± 3%.