A method for classifying an occupant weight of a vehicle is disclosed. When an occupant gets in to or gets off a vehicle, an occupant weight is quickly classified by relatively shortening time for classifying the occupant weight into a certain weight class, and when the weight is changed according to vibration of the vehicle or a movement of the occupant in a state that a vehicle seat is occupied by the occupant, time for re-classifying the weight class is lengthened to thereby prevent frequent re-classification of the occupant weight, and accordingly, the reliability of an occupant weight classification system can be enhanced.