The invention discloses a commercial vehicle mechanical automatic transmission load identification computing method. The method comprises the steps that a shift state is determined; an acceleration, driving force, air resistance and a slope value after the shift are determined; vehicle quality is calculated; whether the calculated vehicle quality meets storage conditions is determined; and if the storage conditions are met, a storage is carried out; the vehicle quality satisfying requirements is stored; whether the stored vehicle quality exceeds a storage limit is determined; if the storage limit is exceeded, the vehicle quality satisfying conditions is taken an averaging value. According to the commercial vehicle mechanical automatic transmission load identification computing method, the acceleration after the shift is calculated, the acceleration is conducted filtering processing, and a ramp sensor is used for obtaining a slope value to calculate ramp resistance, so that the accuracy of the vehicle quality calculation is ensured; vehicle quality dissatisfying the storage conditions are abandoned, so that the accuracy of the vehicle quality calculation value is further ensured and the shifting force in the vehicle shifting process is controlled accurately.