Abstract: The method to combine the GPS data from different analysis centers by SINEX files is introduced.In order to analyze the systematic error,the Helmert transformation parameters are added into the adjusment model in the data processing.The results show that the accurcy of coordinates with Helmert transformation parameters is higher than that of the coordinates without Helmert transformation parameter so as to indicate that the method can elimilate the systematic errors effectively and the systematic errors can also be estimated.