Abstract: In the report， an improved Kalman filter clock synchronization algorithm was proposed.The improved Kalman filter algorithm adopts the untrusted input identification and introduces the deviation index as the threshold value of the untrusted data.When errors occur， the data can be smoothed quickly to prevent the occurrence of major errors. The results of the simulation test proved that the improved Kalman filter algorithm can achieve better clock synchronization accuracy and stronger system robustness， and the master-slave base station clock synchronization performance is greatly improved.