Abstract: Degradative and metabolic routes of fipronil in the model paddy field ecosystem were conducted. The results showed that MB46513 and RPA200766 were main catabolites of fipronil in water under the actions of photolysis and hydrolysis in the model ecosystem; MB46136 and RPA200766 were the majorities among the four metabolites in soil under the actions of oxidation and hydrolysis; MB46136 and MB45950 were only two compounds derived under the actions of oxidation and reduction in rice plant, respectively.