National Time Service Center, Chinese Academy of Sciences(NTSC) has taken the charge of the national standard time UTC(NTSC). The time differences between UTC and UTC(NTSC) has not exceeded ±5ns ever since 2018,which is notable achievements in high precision time-keeping area. The short-term(≤5d) frequency instability of UTC(NTSC) needs to be improved, meanwhile the robustness and accuracy of UTC(NTSC) are also what we want to improve. To achieve this, we modified the timescale algorithm and steering algorithm, which is testified with clock data in our Time-keeping laboratory. Result shows that the time differences between UTC and UTC(NTSC) was always less than 2.5 ns during September 2021, and the frequency instability of UTC(NTSC) is low than 5E-16(5d).