The present invention provides a parallel parked vehicle nighttime detection system. According to the parallel parked vehicle nighttime detection system, the lights of passing vehicles are adopted toilluminate and detect parked vehicles. The system comprises a parked vehicle sensor and a moving vehicle sensor, wherein the parked vehicle sensor monitors a parking area which contains a plurality ofparking spaces, and the moving vehicle sensor senses moving vehicles in the vicinity of the parking area; when the parked vehicle sensor extracts the reflection area of at least one headlight or at least a portion of a front bumper bar when the moving vehicle sensor senses at least one passing vehicle.