Abstract: We put forward a method of using LSSVM to fit the satellites' clock error data,and give the concrete step of the method.For the both ends dissipate phenomenon,we make use of the method of adding window to improve accuracy.The calculate example using the clock error data from IGS shows that the add window LSSVM method has higher accuracy than the existing method,and the polynomial kernel function is the better kernel function than others.At last,we use the adding window LSSVM to fit the clock error data of different satellite clocks.