The invention discloses a motor vehicle overloading determining method. The method includes the following steps: when a traveling vehicle is in contact with a lower pressing plate, the lower pressing plate is driven to move downward and is in contact with a pressure sensor. The pressure sensor transmits pressure data detected to a controller which commands a camera A, a camera B and a camera C to separately photograph the license plates of traveling vehicles which pass by so as to collect overloading of traveling vehicles. The lower pressing plate cooperates with a pressure spring, which can reduce impact on the pressure sensor imposed by transient pressure produced when the contact between a vehicle and the lower pressing plate occurs, and when the pressures measured by the pressure sensor are within different ranges, the camera A, the camera B and the camera C separately photographing the license plates of the traveling vehicle, recording the overloading of the vehicle, helps traffic management departments to punish the overloading accordingly, maximizes the protection of highways and relevant facilities, reduce overloading of vehicles, and keep roads safe and unimpeded.