The invention provides an overhead type impurity detection system between subway platform doors and vehicle doors. The overhead type impurity detection system comprises a door control circuit connected into a safe circuit of the platform doors. The door control circuit comprises door control devices which are arranged corresponding to all the platform doors, are sequentially in series connection and comprise laser scanning sensors and control units. The laser canning sensors are arranged above the platform doors. The scanning ranges of the laser scanning sensors are the spaces between the platform doors and the vehicle doors. The laser scanning sensors are in communication connection with the control units and are mounted below concrete top beams, influence of a limit is small, the detection area can be flexibly adjusted, the requirement that any position between two doors can be detected is met, dead-corner-free three-dimensional area protection is achieved, and any object with the diameter being larger than 8 mm between the platform doors and the vehicle doors can be detected.