Transmission angle γ was an important parameter of four-bar mechanism. The larger the transmission angle γ, the more favorable it was to the transmission of mechanism, and γ changed with the change of the crank angle position. In order to ensure that the mechanism had good force transmission performance, transmission angle should satisfy γmin≥40°. When the minimum transmission angle of centric slider-crank mechanism was located perpendicular to the guide path, the minimum transmission angle could be obtained by the following formula: