The generation principle and meshing characteristics of conjugate-curve circular arc gears, which is proposed based on the theory of conjugate curves, are studied in this paper. The generation principle and mathematical model of this gear drive are introduced according to the given spatial screw curve. Tubular meshing surfaces contacting in the orientation of designated contact angle are provided to build up circular arc tooth profiles, which inherit all properties of conjugate curves. Geometrical three-dimensional models are established based on a numerical example and the results of motion simulation show that the generated gear drive meets general meshing and motion conditions. The comparisons between this designed gear drive and conventional circular arc gearing for the generation method and meshing characteristics are carried out. And the transmission efficiency of gear pair manufactured by hobbing cutter tools is also test. Through the analysis, it shows not only the general corresponding relationship between two gears, but also the conjugate meshing essence of circular arc gears. Theoretical and experimental results demonstrate the feasibility and correctness of proposed conjugate curves theory and the application to new types of gear drive with high performance will be carried out.