Abstract: It is expected to take dozens of hours' computer running time to complete the operation scheme optimization of large-scale natural gas network, and most of the time is spent on the computation of compressor power. It is proposed to simplify the computation of compressor power by using the fitting function, but this method doesn't take into consideration the effect of inlet temperature on compressor power. To increase the fitting precision, the fitting function was modified by introducing the inlet temperature of compressor. Then, three types of compressors installed in a domestic gas pipeline were used to test the performance of the fitting function. It is indicated that the maximum deviation of the fitting function is higher than 10% before the modification and lower than 5% after the modification and the average deviation is lower than 1%. When the modified fitting function is applied to the operation scheme optimization of a virtual gas pipeline, the absolute deviation of the calculation results between the conventional method and fitting function method is less than 0.67 MW and the relative deviation is less than 1.1%. The fitting function method saves much more time than the conventional method.