Abstract: The precision of GPS monitoring deformation for Gehey an Dam is much lower than that of others under the ordinary conditions.Therefore, how to process the data of Geheyan Dam is not only a difficult task, but also a real challenge for us. By analyzing the result s of another reference station,GPS2,we found that there are some differences among the ones of each session, thus it can be seen that there are some errors in the procedure of data processing.It is difficult to deal with these errors.On second thought s, we compute the relative coefficients of GPS2 for each deformation monitoring station, and get a fact that there are strong relativities among GPS2 and monitoring stations.Therefore, we can use the data of GPS2 to lower or eliminate the errors of the deformation monitoring stations. Based the above,we put forward the method as follows:First,make the best use of a mass of raw data owing to around-the-clock observation and use Filtering Method to get rid of gross errors and noises of the deformation monitoring stations.Second, use Integral Adjustment Method to get the result s.It is the critical approach to get a good result.We adopt different weight values for different types of stations, the deformation monitoring stations are endowed with small weight values;GPS2 is endowed with relative to much bigger value;and GPS1 is endued with infinite, i.e. GPS1 is fixed.We cite an example in this paper which proves that the above method is right and feasible.