This paper presented a control strategy of indirect position estimation for switched reluctance motor (SRM) based on the single threshold of pulse injection in order to reduce the application scope of the limitation due to the position sensors. Considering the case of the bus voltage change, through injecting voltage pulse into one idle phase of 6/4 motor, the pulse peak current is detected by the mean sampling method proposed in this paper. The results are then used to predict the position by means of comparing the current preset threshold. After acquiring the time interval between adjacent threshold, it is convenient to calculate the speed and to confirm other position at every time. The deviation between estimated position and actual position was also analyzed. The proposed method not only reduces the negative torque influence brought by injection pulse but also flexibly implements the angle control that optimizes the motor running state. The SRM sensorless speed control system is built in Simulink, and the DSP experiment results verify the present method.