Abstract: The extremely low weathering rate of microplastics in the environment is a current problem, which greatly restricts the understanding of microplastics and limits their research. To accelerate the aging of microplastics and improve laboratory separation, high-density polyethylene (HDPE) was aged by two methods, namely ultraviolet (UV) radiation and UV-activated persulfate (UV+P) treatments. These methods simulated and accelerate the aging of microplastics. During the aging process, separation methods were improved based on microplastics property changes, which increased the separation efficiency. The specific methods are as follows: Put siphon tube into the bottom of the clarified liquid after resting and layering, and vacuum filter the liquid slowly into the filter bottle through the pipe. This method can separate floated microplastics and effectively filter suspended microplastics from clarified liquids. The surface morphology of HDPE was characterized by scanning electron microscopy (SEM). The functional groups and degree of aging were determined using Fourier infrared spectroscopy (FTIR) and the carbonyl index (CI), respectively. The results showed that the UV+P treated microplastics were more hydrophilic than the UV treated microplastics, as shown by the significant difference in separation time (P<0.05). During the aging process, the removal rates of small organic molecules by four cleanings reached 95.29% and 94.71%. The two aged microplastics had high yields of 84.63% (UV) and 86.63% (UV+P) under this separation method. The SEM images showed that the aged microplastics had a rough surface with many cracks and small holes compared with the original HDPE. The two different aging methods may potentially influence the surface morphology of microplastics. FTIR showed that new peaks, mainly attributed to carbonyl and hydroxyl groups, were detected in aged microplastics but were not present in virgin microplastics. CI showed that microplastics can reach a high degree of aging in 5 days, and the Cis were 0.39 (UV) and 0.49 (UV+P). Overall, the two aging methods (UV and UV+P) can obtain microplastics that differ from the original microplastics in terms of hydrophilicity, surface morphology and functional groups. The improved separation method can obtain samples rapidly and efficiently.