In order to improve the satellite laser ranging data accuracy and stability of Changchun Station, analysis was performed with a data assessment system using precise satellite ephemerides. The assessment system was established from physical mechanism and widely recognized evaluation standard of satellite laser ranging, using precise orbit ephemerides as input. With the help of above assessment system, a new method known as the leading edge half maximum (LEHM) algorithm is used to improve the data pre-processing method and reduce the impact of satellite signature effect on data accuracy and stability. Analysis showed that the output of the data assessment system is consistent with those of International Laser Ranging Service (ILRS) analysis centers. After data pre-processing with the LEHM algorithm, normal point accuracy was improved from 4.9 mm to 3.9 mm, short-term stability was improved from 19.8 mm to 18.1 mm, long-term stability was improved from 6.2 mm to 5.4 mm and range accuracy was improved from 79.6 mm to 68.2 mm. The LEHM algorithm can effectively improve the data accuracy and stability, which points out the way to further improve the accuracy and stability of Changchun laser ranging data.