Abstract: In order to determine the CHAMP's orbit,the onboard GPS data of CHAMP,the GPS data of IGS tracking stations,EOP,SGO and time data are necessary.The GPS data should be pre-processed to correct the clock error,solve the ambiguity,detect the cycle slips,determine the satellite attitude,and calculate the antenna phase center offset and correction.Then the air-ground GPS double-difference phase observations are constructed.The CHAMP's orbit is really determined with the dynamic method.Comparing with the PSO from German GFZ,the precision(RMS) in the radial direction is 0.285 7 m.For the 1-day overlapping orbit,the RMS of radial orbit difference is 0.095 8 m.Comparing the orbit endpoints,the mean difference of radial orbit is 0.066 6 m.