Biochemical treatment of pesticide wastewater is difficult accompanied by nonviable microorganisms and low treatment efficiency due to the unique characteristics of the complex components and high biological toxicity of pesticide wastewater. Herein, a highly efficient inoculum was prepared for the degradation of phoxim. The application of inoculum on the treatment of phoxim pesticide wastewater was investigated. A highly efficient phoxim-degrading strain was obtained through the acclimation of phoxim-specific strain in an inorganic salt medium containing 400 mg/L phoxim and 1.0 g/L glucose. The degradation rates of phoxim with initial concentrations of 21.5 mg/L and 50.5 mg/L reached 75.84% and 73.36%, respectively. Inoculum was prepared using the mixture of wheat bran, sawdust and diatomite at the ratio of 80:10:10 (mass ratio) as carrier. The inoculum has the bifunctional advantage of adsorption and degradation to phoxim. The degradation kinetics showed that the degradation rates of phoxim at the initial concentration of 200 mg/L and 400 mg/L reached 75.84% and 73.36% within 10 hours, respectively. The good effect on the removal of phoxim and the wastewater quality purification can be realized when the inoculum was used in sequencing batch reactor activated sludge process to treat pesticide wastewater. This study provides technical means and theoretical foundation for the biological treatment of phoxim pesticide wastewater using a microbial inoculum.