The invention discloses a prompting device for an illuminating lamp in a power plant. The prompting device is used for accurately detecting illuminance of the illuminating lamp in the power plant. The prompting device comprises an illuminance detector fixed to a mounting surface, and further comprises a second bracket, a swinging driving mechanism and a third bracket, wherein two rotating shafts arranged on the left and right are rotatably mounted on the second bracket; a first swinging rod is fixed to the rotating shaft on the left; a second swinging rod is fixed to the rotating shaft on the right; the swinging driving mechanism used for driving the first swinging rod is arranged on the second bracket; the third bracket is arranged at the lower ends of the first swinging rod and the second swinging rod; a vertical shaft is rotatably mounted on the left side of the third bracket; a rotation driving mechanism used for driving the vertical shaft to rotate is arranged on the third bracket; clamping pieces are fixed at the top of the vertical shaft; cleaning brushes are arranged on the inner sides of the clamping pieces; the volume of a cavity defined by the plurality of clamping pieces in the natural state is smaller than the shape of lamp; the illuminance detector is in signal connection with a controller; and the controller is in wireless communication with a mobile terminal of an administrator through GSM. According to the device, the lamp illuminance can be effectively detected.