Abstract: Time interval counters are widely used in time and frequency calibration. Aiming at the measurement of metrological characteristics of rubidium frequency standard and cesium frequency standard, a time offset measurement system based on SR620 was designed to measure the relative frequency offset, frequency stability and daily frequency drift rate, and draw the frequency stability curve and frequency drift rate curve. The experimental results show that the measurement results of the system are expected and can be used for time and frequency traceability and calibration.