The invention discloses an offset worm and wormwheel transmission designing and manufacturing method. The offset worm and wormwheel transmission designing and manufacturing method comprises the following steps: a. determining a gear face equation of the worm according to an actual machining parameter and a worm design principle; b. obtaining a gear face equation of the wormwheel according to the gear face equation of the worm and a gear face meshing principle and according to the installing position of the worm and wormwheel; and c. carrying out tooth direction and tooth profile shaping to the wormwheel so as to drive the worm and the wormwheel to form point contact that the contact area is elliptically shaped, and the long axis direction of the contact area is perpendicular to the relative movement direction of the gear face of the worm and the wormwheel so as to form a beneficial contact condition of extreme pressure lubrication. According to the method, after the worm and the wormweel which are meshed mutually are designed, the worm is shaped, so that the gear face is meshed to be point contact; the meshing moulage is adjusted conveniently; the installation error is absorbed; and at the same time the contact area of the worm and the wormwheel is elliptically shaped and the long axis of the contact area is perpendicular to the direction that the gear faces of the worm and the wormwheel move relatively, so that the worm and the wormwheel which are meshed mutually are under lubrication in a good state.