The invention discloses a heavy vehicle weight real-time identification method based on CAN information and a function principle. According to the method, when a vehicle runs, vehicle wheel speed, engine rotating speed, engine practical torque percentage, a gear position, accelerating pedal opening degree, a clutch pedal signal and a braking pedal signal are acquired through a vehicle CAN bus; engine torque, accelerated speed and a rotating weight conversion coefficient are obtained by computing; a vehicle longitudinal kinetic equation based on the function principle is established, on the basis of the kinetic equation, the work done by equivalent outer force generated by driving force and air resistance is regarded as system input quantity, the work done by the equivalent accelerated speed generated by the sum of rolling resistance, slope resistance and acceleration resistance is regarded as an observable data vector, and heavy vehicle weight is estimated in real time through a recursive least-squares method with which a forgetting factor is selected according to the feature of the vehicle weight.