Alignment errors are important influential factors to the gears' contact quality.The general model of the spiral bevel gears' tooth processed by cutter-tilt method and modified-roll method was proposed.Method of tooth contact analysis including alignment errors was established.Effects by alignment errors were investigated

the conceptions and models of alignment errors sensitivity and tolerance were proposed.According to parameters design of the gears

the effect laws and tolerance of the alignment errors could be obtained by using this modified contact analysis algorithm.Simulation analysis shows its feasibility.Alignment error sensitivity

tolerance of the alignment errors with the corresponding calculation methods could reflect the internal influence of spiral bevel gears' contact quality and installation technology due to alignment error.The research can provide a theoretical basis for improving the design quality of the spiral bevel and hypoid gears and developing the scientific installation technology.