Abstract: Regarding the evaluation of satellite orbit lifetime under effect of atmospheric drag, a highly efficient numerical method called differentiation integration method is proposed. The essence of this method is a group of differential equations based on the average change rate of orbit elements, and the right sides of these equations contain definite integrals. The calculation comparison between this method and the traditional ones proves its correctness and displays its high efficiency. This method is very powerful especially for problems concerning space debris mitigation that require a large amount of calculation of the satellite orbit lifetime.