The worm drive is last stage reduction gear of one antenna deployment mechanism, and the load beared by the worm gear is the maximum. The reliability of worm gear is critical for the successful deployment of the antenna. In order to improve the reliability of mechanism by controlling the worm assemble errors, this paper studies the contact stress sensitivity to different assemble errors. First, the 3D tooth contact FE model of worm gear is established. Then based on three kinds of errors for worm assembling and according to the center distance deviation, middle plane deviation and axis angle deviation, five work conditions are formed. Finally, the contact stress for each work condition were analyze, results demonstrate that the axis angle deviation will affect contact tress most seriously.