Utilizing an asymmetric magnetic field caused by a mechanism design between a motor rotor and a stator to induce a BEMF, a method for starting a fixed rotation direction of single-phase sensorless DC brushless motor, includes: power-on starting a motor control circuit; if the motor is not in a rotating state before starting the excitation, executing a static starting procedure; then, if the motor rotation direction conforms to a predetermined direction, executing a normal driving procedure; otherwise, executing a static starting procedure. The static starting procedure, by discharging remnant energy of the motor, achieves the purpose of star-up by performing the steps of first phase excitation, stop excitation, and strong second phase excitation. In the normal driving procedure, the slope of BEMF signal of the first phase or the second phase is taken out periodically to detect the motor rotation direction.