To satisfy the requirements of high accuracy and high-loading capacity, a novel precision-power hourglass worm drive characterizes with backlash-adjustable and wear-compensable is demonstrated. This hourglass worm drive is consisted of an involute helical beveloid (IHB) gear and a toroidal involute (TI) worm generated by the IHB gear tooth surface, and the material of IHB gear is bearing steel, as well as the material of TI worm is structural steel. For this hourglass worm drive, mathematical model is developed, basic equations are derived, and tooth contact analysis (TCA) is simulated by computerized calculation examples. Theory of backlash-adjustable and wear-compensable of this hourglass worm drive is derived. The high-loading capacity of this novel hourglass worm drive is confirmed by the TCA and stress analysis. This study is expected to provide a theoretical foundation for the future industrial application of this novel backlash-adjustable and wear-compensable hourglass worm drive.