In this paper, a FPGA-based step motor driver implementing adjustable subdivision and sine pulse width modulation is introduced. This driving system can solve the high subdivision problem, increase the driving torque and angle resolution, and smooth the motor angle. Employing the bottom-top design method, the circuit was described by the VHDL language, synthesized by Xilinx ISE integrated environment, and simulated by Modelsim in both behavior level and gate level through the PLI interface. According to experiment’s result, this driver has the advantages of easy debugging, high anti-interference ability, larger driving power, low volume and low cost in large scale production.