By traveling in the space between the leading edge, the trailing edge and the web of the wind turbine blade, the robot detects the defects of the adhesive between the front beam, the rear beam and the shell and the hollow, crack and crack of the reinforcement glue in the web, as well as the cracks, whitening and wrinkles of the inner skin and the middle main beam cap of the web. Going deep into the blade cavity can reach more than 85% of the blade length.