Brushless DC motors (BLDCMs) are widely used in electrical drive field. As neutral point exists in conventional star-connected and delta-connected BLDCM windings, torque ripples and low reliability may happen to the motor. The application of open winding to three-phase BLDCM system is proposed. The topology and 8 operation modes of open-winding BLDCM system are introduced. The electromagnetic equation of open-winding three-phase BLDCM is analyzed. A mathematical model of the open-winding BLDCM is built with MATLAB Simulink toolbox and the current, torque and speed of the motor under 8 operation modes are simulated. The prototype and the test system are designed. The performances of open-winding BLDCM in two-phase conduction and six-state operation mode are tested. The test results show that，compared with star-connected BLDCM, open-winding BLDCM has a wider speed adjustment range and less commutation torque ripple, exhibiting similar torque-speed characteristics.