Abstract: Aiming at less use of GAMIT software to analyze the BeiDou baseline, firstly we use the GAMIT software to calculate the BeiDou long baseline, then select the cutoff height angle, the zenith troposphere delay parameter, the three control parameters of the measuring station constraint value to test the effect of the BeiDou long baseline solution. The results show that the GAMIT (10.61) can successfully solve the BeiDou long baseline and the relative precision is 10^-8 magnitude; the selection of the cutoff height has a great influence on the resolution accuracy, and the setting of the number of the delay parameters of the zenith troposphere has little influence on the solution, but the resolution accuracy also improves with the increasing of the number. It is very important to choose the appropriate constraint value to set the different constraint values of the station to influence the baseline accuracy.