The traditional design and analysis method for the eccentric involutes gears transmission has model error. Some important parameters, such as minimum geometrical center distance and eccentricity, are not calculated accurately. The differential equation of eccentric involute gears transmission is established on account of the geometrical relationship of eccentric involute gears transmission. A calculating method of the geometrical center distance and eccentricity are derived. The relationship between the minimum geometrical center distance or maximum transmission ratio and initial meshing angle and eccentricity are analyzed. The minimum geometrical center distance and eccentricity are fitted by polynomial. The analysis and design can be completed fast and accurately by using polynomial fitting formals, so the process of analysis and design are simplified.