Abstract:The independence of time and frequency standards is an important basis for the comprehensive PNT system construction in China. To further evaluate the timekeeping capability of the atomic time scale based on the national primary frequency standard, the improved FIR clock difference prediction and frequency control method is used to post-process the frequency difference of the cesium atomic fountain clock relative to the hydrogen maser. By post-processing, the autonomous time scale and traceable time scale are generated respectively. The two-time scales are compared with UTC by the international atomic cooperation link. The long-term experimental results show that both of the time differences between the two-time scales and UTC are less than ±4 ns and the frequency stability is less than 8×10 -16 / 5 d from December 2021 to December 2022.