An improved bond-based Smoothed Particle Hydrodynamics (IBB-SPH) method is developed to simulate the crack propagation and failure process of rock slopes under seismic conditions. In the IBB-SPH framework, an improved cracking and block contact method is proposed. For carking, the kernel function of damaged particles is modified by complete bonds broken. Simultaneously, contacts are established between particles, enabling contact sliding and rotation between damaged particles and intact particles. Uniaxial compressive tests of rock cells considering different heterogeneity have been conducted to verify the accuracy and feasibility of IBB-SPH. Furthermore, the whole progressive of cracking, sliding and crash failure, and deposition of the Daguangbao landslide are simulated under Wenchun seismic wave. The results indicate that the IBB-SPH enables to simulate the crack initiation, propagation and coalescence of rock masses. Additionally, it can accurately simulate the contact behavior between particles, providing a realistic representation of the crack propagation, frictional sliding, and deposition of the Daguangbao landslide under seismic conditions. Moreover, compared with other mainstream discrete numerical algorithms, IBB-SPH exhibits higher efficiency in determining and validating macroscopic physical parameters of the rock, which can be applied to simulate the crack propagation and contact behavior of discontinuous rock masses on the engineering scale.