In order to simplify the structure and improve the accuracy, this paper designs a phase laser ranging system based on FPGA. The system chooses the method of phase laser ranging, with the FPGA as the core processor, and completes the hardware and software design based on the principle of dual frequency modulation and difference frequency measurement, which can realize the ranging function in complex environment. The hardware of the system includes the laser modulation circuit, photoelectric detection circuit, frequency synthesis circuit and mixing circuit. The software design includes the generation of PLL modulation signal, the control of laser transmitting and receiving module and the distance analysis and calculation. By comparing the phase difference between the received laser and the emitted laser and calculating the distance, the whole ranging process can be realized. By analyzing the waveform measured by the experiment, the range of the whole ranging system can reach 60m, and the accuracy is within mm. The system has the advantages of good stability, simplified complexity of circuit design, low cost and high integration.