Abstract: The original data of the GPS stations in the Crustal Movement Observation Network of China was processed. We adopted two different data processing methods differ in choosing reference coordinators to process the data. Part of ITRF stations which are superior in stability were selected in the first method and the ITRF stations in the neighborhood were selected in the second. Comparison of the result through processing the data relatively, systematic deviations have been found between the two results. The reulsts show that the magnitude and characteristics of the systematic deviations act differently in different directions, and the functional mechanism is relative to the spatial and temporal distribution of the sites. Through analysis on the phenomena and findings refered, some relative conclusions are derived and the advices on establishment of regional coordinate system are also given.