Orthogonal variable transmission ratio face gear drive is a new kind of gear transmission. The equation of the pitch curve, addendum curve and dedendum curve of face gear were established on the basis of spatial transformation relations and principles of gear. The parametric equation of tooth surface of the face gear was obtained by combining the parametric equation of cutter's tooth surface and conjugate tooth profiles theory. The calculation method of tooth width was derived on the basis of root cutting and tapering conditions. The space trajectory of the tool in the machining process was analyzed and the parametric design and machining simulation system of orthogonal variable transmission ratio face gear were developed on the basis of the environment of VB and Solidworks (API). Finally, experimental study was carried out on the orthogonal variable transmission ratio face gear pair to verify the validity and feasibility of the theoretical derivation and parametric design and machining simulation of the variable transmission ratio face gear pair.