Switched reluctance motors (SRM) are used for low-cost variable-speed drives in many industrial applications because of their desirable features: simple construction, high reliability and low cost. However, a traditional position sensor is needed for its control. Sensorless driving methods have attracted much interest. We have proposed a simple and practical sensorless driving method using an impressed voltage pulse at an unenergized phase. This method is based on the inherent magnetic characteristics of SRM: the magnetic circuit changes with the rotor position and has several advantages: one phase pulse injection brings a simple structure and a new exciting timing method eliminates the negative torque. But the proposed method is limited to constant speed driving. In this paper, we extend the proposed method into a variable speed control sensorless driving method as well as inheriting the above advantages.