The invention discloses a detector with a stable heat radiation structure. The detector with a stable heat radiation structure comprises a housing, a top cover, a sheet metal part, a circuit board, a lens and a tail circuit, wherein a processing chip is arranged on the circuit board; the upper end surface of the processing chip is connected with a radiating fin; and the radiating fin is fixedly connected with the circuit board. As the detector with a stable heat radiation structure substitutes the radiating fin structure for a fan structure, the space is saved and the requirement for stability of the product is satisfied and the radiating fin is preferably fixed on the circuit board. At the same time, the detector with a stable heat radiation structure can intelligently detect pedestrians who enter a tunnel and can give an alarm timely to avoid occurrence of traffic accidents, thus being significant in maintaining the traffic order and guaranteeing traffic safety. And, the detector with a stable heat radiation structure also has the advantages of saving the cost for manpower monitoring, being high in the precision for detection and the reliability for detection, being low in the cost of the device, being simple and convenient in installation, being high in robustness of the detection algorithm and being high in intelligence degree.