Tooth contact analysis（TCA）is solve the nonlinear equations according to the surface parameters of machining parameter selection of reference point for the initial valueTooth contact analysis（TCA）is calculated the surface to solve the nonlinear equations

finally the tooth contact trace and transmission error is got.While using duplex spread blade

it does not need to set the reference point

the initial value can’t be given

it is difficult to solve nonlinear equations for TCA of duplex spread blade.According to the particularity of duplex spread blade

a way to select the initial point is designed

TCA of duplex spread blade is completed

the tooth contact trace and transmission error are got

the tooth contact conditions is intuitively reflected

the problem that TCA does not apply to duplex spread blade is solved

the theoretical basis for practical production and processing is provided.