A positional parametric analysis of contact pattern is put forward,which can be used for determining the variation range of installation errors of spiral bevel gears.For forming the tooth surfaces of spiral bevel gears,manufacture parameters are designed based on local synthesis to meet design specifications.The pinion drive torque is calculated with indentation depth 0.006 35 mm at the mean contact point on single mesh tooth surface.Loaded tooth contact analysis(LTCA) is performed under this torque with installation errors,and the positional parameters of contact pattern are obtained.Taking the distance between the contact pattern and predetermined tooth surface boundary as design objectives and different types of single factor installation error as design variables,optimization is applied to find the range of installation errors when the contact pattern traveled within the tooth surface boundary.Taking a pair of spiral bevel gear in accessory drive system on aero engine as an example,the variation range of different types of installation errors is ascertained,which validates the effectiveness of the proposed method.The proposed method provides a reference on determining the variation range of installation errors for spiral bevle gears.