The continuous accumulation of microplastics (MPs) in water, soil, and atmosphere will pose a serious threat to the environmental ecological balance. How to reduce and eliminate MPs in the environment has become a hot issue. Here we isolated Bacillus cereus CH6 from lake sediments and investigated its ability to degrade polystyrene microplastics(PS MPs). Bacillus cereus CH6 has short generation time, high activity, and fast substrate utilization. The weight loss was 10.7% by Bacillus cereus CH6 after 50 days of incubation. Moreover, the average degradation rate reached 0.967 mg/d. We further investigated the surface morphology changes and the internal structural changes during the degradation of PS MPs. Finally, the changes of bacterial protein concentration and esterase activity during the PS MPs degradation process were observed from the perspective of biological index changes. These results are expected to provide a new candidate for PS MPs degradation.