Abstract: Due to the long-term operation of wind turbines, excessive wear of brake pads of yaw brake system results in oil leakage of yaw brake system of wind turbines, breakage of brake bolts, and even damage of brake pads. Based on this, the brake pad detection device of yaw brake system is designed. The device consists of a signal power supply, a micro stroke switch, a stroke switch base and a digital input point of a codeable logic controller control system for wind turbines. The device is applied in Hengrun wind farm of Inner Mongolia Hengrun New Energy Co., Ltd., which greatly improves the reliability of yaw system, reduces the operating cost of enterprises and ensures the safe and stable operation of units.