Involute beveloid gear is one of the involute spur gears .It can be work with parallel axes, intersecting Axes, crossed Axes. Lateral clearance of the gear transmission backlash can be controlled by adjusting the relative axial position of involute beveloid gear transmission pair between two gears. It make a very small backlash or zero backlash .It can be used in backlash-free precision transmission .Its manufacturing is easy and its load capacity and transmission is high. In different cross-section with a different modification coefficient is its geometrical characteristics. The most important par of design involute beveloid gear is to choose a reasonable modification coefficient. In this paper, the beveloid involute gear's design process is introduced to choose its modification coefficient in satisfying various conditions, such as the gear teeth not to undercut, the addendum not to sharpen, guarantees coincidence degree. And uses the VB language to establish a design platform of the external transmission of involute beveloid gear with parallel axes .It is suit for project application. First，chooses modification coefficient by not to undercut, not to sharpen, guarantees coincidence degree.Next, compute the related geometry size. Third, according to the computed result, draws up the tooth profile curve in SolidWorks. Thus produces the gear's tooth profile or the socket gallery precisely, make gear's 3D modeling. It provides the basis for gear's optimization design and advanced manufacture. A new gear is rapidly established by change gear parameter in the designs platform. It can greatly raises r the efficiency and the precision of design involute beveloid gear, which provided the precise model for its dynamic simulation, the NC processing, the interference examination as well as the finite element analysis. Introduce the use method of design platform through a practical example confirms its usability.