The purpose of this study is to analyze the dynamic characteristics of cracked blades of aero-engines, improve the reliability of aero-engines and minimize the occurance of catastrophic accidents. This study is based on the strain energy release rate and Castiglianos theorem, combined with Timoshenko beam theory, a new stress intensity factor and flexibility matrix of the cracked beam element is derived, considering the effect of the angles of the slant crack. According to the stress change of the cracked surface during vibration, a method is proposed for calculating time-varying stiffness of the cracked beam element based on the contact area of the cracked surface. A dynamic model of the slant cracked twisted blade with breathing effect is established. By comparing the natural frequencies and vibration responses obtained by the proposed model and the finite element model of the ANSYS Solid186 element, the validity of the proposed model is verified. The results show that as the crack angle increases from 0° to 80°, the natural frequency increases by approximate 3%, that is, as the crack angle increases (the crack front is closer to the blade tip), the natural frequency of the cracked blade increases. Additionally, as the crack angle increases, the vibration displacement amplitude of the rotating cracked blade decreases. The amplitudes of the constant component and the multi-frequency in the spectrum also decreases. Furthermore, the amplitude of the 1.0f_e under the first order resonance state is reduced by about 40%. The calculation speed of the dynamics response of the proposed model is faster than that of ANSYS model, with an improvement of about 22 times.