Abstract: Introduced the system architecture and key technologies of high precision time interval measurement based on Field Programmable Gate Array (FPGA) , which produce associated multiple reference clock by frequency, phase shift used PLL.For short intervals along the sampling measurement by both edges, which is equivalent to increase clock frequency, reduce the quantization error, increase the time interval measurement resolution with 625 ps optimization has been achieved in the measurement range more than 20s, which provides narrow range for ultra precise time interval measurement, thus the new precise measurement is more useful for focusing on the higher resolution and accuracy.