This paper intended to derive the equation of the teeth surface of the involute arc cylindrical gear. Based on the forming principles of the teeth surfaces of the spur cylindrical gear and the helical cylindrical gear, an arc line parallel to the axis of the cylinder was firstly drawn in the generating plane, and then the scanning surface of the arc line should be the teeth surface of the involute arc cylindrical gear. After that, the equation of the arc line was derived and then the teeth surface. Finally the simulations of those equations were described with the instruments of proeWildfire 5.0 and MATLAB R2010a. Thus, the correctness of the equations was further proved.