A power transmission mechanism of twin-rotor engine based on wobble plate and cam was proposed. The advantages of the power transmission mechanism of twin-rotor engine based on wobble plate and cam are simple structure, completely symmetrical arranged, good balance, and the movement is controllable. For analyzing its operating characteristics, the basic kinematic model was established by Euler-equation, and its trajectory and cam contour lines were obtained. Effects on volume variation of the main structural parameters, such as plate inclination angle and roller axis angle were analyzed. Main results are as follows: the closer to 90° roller axis angle is, the larger volume variation is. Plate inclination angle is proportional to volume variation. For 4-blade pistons rotor, the maximum plate inclination angle is approximately 65°. In practice, the best roller axis angle is 90°, plate inclination angle should be large enough after taking the thickness of blade piston into account.