In this paper, the reduced master equation which is a fast simulation method of spin dependent transport in ferromagnetic single electron transistors is presented, for first time. This simulation method follows steady state master equation in which all charge states of the system are considered, whereas charge states are decreased in reduced master equation. This method is based on two degrees of electron freedom which are charge and spin. This is applied in the condition that orthodox tunneling theory is applicable to calculate the tunneling rate of electrons through barriers. The comparison between the I-V characteristics of a ferromagnetic single-electron transistor by following the reduced and full master equation methods for different main parameters of these transistors show that the results are exactly the same at low bias voltages. Consequently, the reduced master equation method is not only more simplified and improves the speed of numerical simulation, but also the modeling results are as accurate as the results of the full maser equation method at low bias conditions.