Abstract Considering a crank-slider mechanism, the analysis of the longitudinal and transverse vibration of the cracked flexible connecting rod is analyzed in this study. First of all, the connecting rod is assumed as the Euler’s beam, then the equations of motion and boundary conditions are derived by using Hamilton’s principle. Moreover, by using the Galerkin method with mode shape function that satisfies the boundary conditions, the equations of motion are reduced to the Mathieu equations. And then, Runge-Kutta method is employed to determine the transient amplitude, some parameters, such as the ratio ( ) of rotating angular velocity of the crank to natural frequency of transverse vibration for the link without crack, the ratio ( ) of the crank length to connecting rod length, and the ratio (a / R) of crack depth to radius of link, influence the amplitude. The results reveal that the natural frequency of connecting rod is not influenced by the angular velocity. While the ratio of the crank length to connecting rod length increases, the transient transverse amplitude increases, too. The ratio of crack depth increases, the transverse amplitude increases a little.