Based on the torsion deformation the gear body and the contact deformation of tooth surface, the fundamental equations of load of the gear was presented, thus established the theoretical basis of the load derivation of the gearing. In this paper, the torsion deformation of the circular arc gears is analyzed first. Then the second order differential equation for the tooth surface load distribution of the involutes gears has been deduced. ompound gearing means more than 2 gears are in meshing with each other. For example, gear1 drives gear2 while gear2 inturn drives gear3. This paper deals the load deviation in this situation.