The present invention relates to a control device and method for adjusting speed and forward/reverse rotation of a wire-controlled brushless motor power supply during positive/negative half-cycle phase loss, comprising an AC power supply, a wire-controlled circuit control device, a brushless motor control device, and a ceiling fan brushless motor, wherein the AC power supply is electrically connected to the wire-controlled circuit control device which is electrically connected to the brushless motor control device and which is electrically connected to the ceiling fan brushless motor, to control the AC power supply positive/negative half-cycle on/off and to generate a positive/negative half-cycle signal for multi-step speed and forward/reverse rotation control, detection, determination, and storage. The overall design is simple and convenient without the need for complicated and cumbersome wiring or safety concerns, to achieve the effect of structural stability and the use of safety and convenience.