For the demand of wind turbine blade adaptive grinding device, this paper proposes an adaptive constant force grinding device with fuzzy PID control based on online sequential extreme learning machines (OS-ELM), by combining OS-ELM to rectify the control parameter input of fuzzy PID controller more quickly, and then get the suitable KP、KI、KD input initial values by fuzzy rules to achieve the PID control parameters are adjusted online. The simulation model of the grinding head control system is validated and optimized by MATLAB/Simulink simulation software, and finally the system control efficiency, stability and grinding effect are tested by the device prototype experiment. The experiments concluded that the device is capable of constant force bright surface grinding of wind turbine blades, the grinding efficiency is significantly improved, and the roughness of the product after grinding is between 10~12 μm, which meets the requirements of the enterprise after grinding blade roughness.