It is an expedient and efficient method to simulate the output power characteristics of a laser diode through the numerical analysis. In this paper, firstly, based on the rate equations of the electrons transition in the active layer, the functions of some key parameters, such as internal quantum efficiency, threshold current and leakage current, etc., are defined with the variance of working temperature. And an accurate numerical analytical model is built by adopting the low-complexity difference method. Then, the simulated results are compared with the results from testing and Optiwave3.0 software. The results show that, by using the proposed analytical model, the simulation on the output power characteristics of a laser diode can be realized in all input current fields, which overcomes the drawbacks within the Optiwave3.0 software. At the same time, the mean deviation between the simulated results and testing results is reduced obviously, and the average error is only 3.88%.