The utility model provides a vehicle detecting system, including traffic flow detector, the line of rabbet joint is seted up on half road surface that keeps left or keep right on every car moving walkways, installs traffic flow detector in the line of rabbet joint, traffic flow detector installs in the line of rabbet joint, and its top flushes with the road surface, traffic flow detector's shell includes four sides and bottom surface, and shell open -top will go up surface closed through the top cap, through a plurality of one -level spring -supporteds between top cap and the shell bottom surface, put at top cap central point and be connected with the sensitive pressure sensor who fixes in the shell bottom surface through a second -level spring, sensitive pressure sensor's output voltage with predetermine the threshold value and carry out the comparison at the comparator, be higher than when predetermineeing the threshold value as sensitive pressure sensor's output voltage, the comparator output high level, the counter is counted the quantity of high level, the counting value sends for the host computer through wireless dispensing device. The utility model discloses a little to road surface destruction during the vehicle detecting system installation, it is simple and convenient to construct.