This research is about a monitoring GPS to monitor the deformation in Jatibarang dam located at Gunung Pati, Semarang, Central Java using GAMIT 10.5 software. The research method is using GPS dual frequency at six points of monitoring which located at the main dam. The technique of analyzing data in this research is using Scientific Software GAMIT 10.5. This research takes in three times period starts from March, May, and finish in April 2014. The research has some purposes and the first purpose is to know the deformation situation that occurred in Jatibarang dam, the second is to find out how to monitor the deformation in Jatibarang dam carefully by using GPS dual frequency, and the third purpose is to know a precision in analyzing data with using Scientific Software GAMIT 10.5 on deformation monitoring. The researcher takes the overview of the libraries in his research such as Dam, Deformation, GPS, The method of monitoring dam deformation, the principles of monitoring dam deformation by using GPS, TEQC (Translation, Editing and Quality Check) and GAMIT/GLOBK. The implementation of this research includes collecting of data by using monitoring to survey GPS and analyzing data with using post-processing method. After analyzing GAMIT and GLOBK then it gets an displacement coordinate value with averages displacement coordinate value on X axis = 0,879 mm, Y axis = 0, 614 mm and Z axis = 1, 114 mm , hence the final conclusion of this research is Jatibarang dam experienced displacement coordinate value in numerical. The resulted test statistically with reliance up to 95% that six monitoring points of the dam are not have displacement point significantly. The conclusion of this research is Jatibarang dam is not deformed.