Abstract: Aiming at the drawbacks of common worm gearing, this article proposes one kind of special form of the new worm-drive: non-backlash double-roller enveloping hourglass worm gear.The structure and the working principles of this worm gear are introduced.After analysis of all factors impacting strength and work-life of the non-backlash double-roller enveloping hourglass worm gear, an optimization calculation model is established by applying equi-strength principle.With the solution of the bound minimization of toolkit in software Matlab-fmincon, the optimal solution is worked out, and the optimization of the main geometry parameters of the worm gear is finished.