The invention relates to a method and system for setting the rotation direction of a brushless motor for an unmanned aerial vehicle. The method comprises the steps of cutting off a power supply connected to the brushless motor when a rotation direction setting signal is received after the brushless motor is powered on; detecting whether the brushless motor rotates or not under the action of an external force after the power supply is cut off; if so, collecting a current signal of the brushless motor when rotating under the action of the external force, and obtaining the rotation speed and thecurrent rotation direction of the brushless motor according to the current signal; and setting the current rotation direction to be a driving rotation direction when the rotation speed exceeds a preset value. Users can enable an electronic speed controller to set the default driving rotation direction of the brushless motor according to the manual rotation direction through simply sending the rotation direction setting signal and manually adjusting the rotation of the brushless motor, and need not to change a line connecting the brushless motor and the electronic speed controller, thereby being capable of greatly shortening the installation time, and improving the installation efficiency of the unmanned aerial vehicle.