Water pollution caused by plastics from household waste is becoming an increasingly significant social problems. In this study, plasma reaction system in solution was introduced to degrade PMMA microplastics. The study investigated how varying power supply parameters such as applied voltage and frequency, as well as the quantity of hydrogen peroxide present in the reactant solution, affects the rate of degradation of PMMA. Chemically active species, such as hydroxyl radicals generated from plasma reaction, were used to degrade PMMA microplastics in the reactant solution. The degradation rate of PMMA particles was increased proportionally with the voltage and frequency of the power supply. This increase in PMMA degradation rate was attributed to the higher electrical energy supplied to the plasma reactor, which facilitated the formation of a plasma field and promoted the generation of chemically active species. the addition of hydrogen peroxide increased the amount of chemically active species generated from the plasma reaction in solution, leading to an increase in the degradation rate of PMMA particles. However, an excessive amount of hydrogen peroxide acted as a scavenger for hydroxyl radicals, thereby impeding the degradation of PMMA particles. This study demonstrates the potential of plasma reaction system in solution as a treatment method to remove the microplastics from aquatic environments.