Abstract: Microplastics (MPs) contained 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 the typical oxidation process for water treatment, polyamide 66(PA66) and polyethylene terephthalate (PET) were selected as the research objects to analyze the DOM precipitation rule of typical industrial MPs in the simulated water treatment oxidation process (UV, UV/H₂O₂, O₃). The results showed that: (1) The three oxidation processes all accelerated the leaching of MPs-DOM, and the DOM leaching yield (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, 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 and then decreasing rule, and among the three types of oxidation systems, O₃ technology had a relatively better oxidation effect on type 2 MPs. (3) The fragmentation effect of O₃ oxidation on MPs is relatively higher. There is no significant difference in the functional groups of MPs surface before and after oxidation treatment, and the carbonyl index (CI) of MPS increases to a certain extent. (4) The DOM derived from MPs was characterized by three-dimensional fluorescence parallel factor analysis. The results showed that the DOM produced by PA66 and PET were similar in the composition of functional groups and fluorescence components, and were mainly composed of tryptophan, tyrotaxine and soluble microbial metabolites.