The deformation and failure process of bearing materials involves coupled actions at multiple scales. It's difficult to reveal the deformation and failure mechanism of materials by only analyzing at the macro scale. It's necessary to comprehensively consider the damage characteristics of the main bearing materials under multi-scale effects, to reveal the typical failure evolution process of bearings from micro to macro scale. Using molecular dynamics (MD) simulations, we analyzed the damage mechanism of crack initiation and propagation in the matrix of 8Cr4Mo4V alloy. The study of the polycrystalline model verified the micro-scale inverse Hall-Petch relation, where material strength decreases with grain refinement. Phase transitions caused by dislocations lead to stress concentration at specific grain boundaries, becoming the main inducer for the nucleation of initial voids. By introducing voids into the model, we investigated the propagation mechanism of micro voids and the weakening effect on the material with different positions and shapes, demonstrating the independence of voids shape in MD simulation. Being able to more accurately simulate the polycrystalline structure and defect types in actual materials, and gain a deeper understanding of the damage and failure mechanisms of materials at the microscopic level.