Due to the shortage of complete design material and mature manufacturing method, less teeth gear (1-7 teeth) transmission has many restrictions in practice nowadays. In this paper, applying the principles of using rack cutter to cut involute gear by using generating methods, we established the dynamic coordinate system and the static coordinate system. By using coordinate transformation method, we derived the equations of gear profile involute and dedendum transition curve. After using Pro/E to plot the end profile of less-teeth gears, we did the 3D modeling and the simulation of the less teeth gear. We also improved a general hobber machine and manufactured less teeth gears successfully. The derivation method of gear profile curve in this paper has lucid concepts which make it quite clear and easy to understand, therefore, it provides theoretical basis to the design, the manufacturing and detection of the less teeth gear.