Abstract: Microplastics (MPs) in surface water can pose potential risks to the aquatic environment and water treatment processes by releasing dissolved organic matter (DOM) as they age and degrade. In order to investigate the ageing characteristics and organic matter release of MPs in typical oxidation processes of water treatment, polyamide 66 (PA66) and polyethylene terephthalate (PET) were used to analyze the DOM release of typical industrial MPs in the simulated water treatment oxidation process (UV, UV/H₂O₂, O₃). The results showed that: (1) All three oxidation processes accelerated the leaching of MPs-DOM, and the DOM leaching rate (calculated as dissolved organic carbon DOC values) of PA66 was higher than that of PET. (2) In the control group, UV oxidation system and O₃ oxidation system, the DOC values of PA66-DOM and PET-DOM showed an increasing trend with the increase of reaction time and oxidizer concentration, while in the UV/H₂O₂ system, DOC values showed a first increasing trend and then decreasing trend. Among the three types of oxidation systems, O₃ technology had a relatively good oxidation effect on type 2 MPs. (3) The fragmentation effect of O₃ oxidation on MPs was relatively high. There was no significant difference in the functional groups of MPs surface before and after oxidation treatment, and the carbonyl index (CI) of MPS increased to a certain extent. (4) The DOM produced by PA66 and PET was similar in the composition of functional groups and fluorescence components, and was mainly composed of tryptophan, thyrotoxin and soluble microbial metabolites. Therefore, industrial grade MPs represented by PA66 and PET will precipitate DOM during the advanced oxidation water treatment process, which has a potential impact on the disinfection and other processes of the backend.