The tooth edge contact of face gear drive with spur pinion isunavoidable. The meshing of face gear drive with spur pinion is investigated. A mathematical model and a constraint condition are developed

by which the contact points on tooth edge could be obtained. The principle curvature directions of contact point on both tooth surfaces are determined with its adjacent meshing points when the edge contact is occurred. The results show that tooth edge contact is happed possibly when both tooth meshed beginning and in that point the transmission error is not equal to zeros.