Abstract: The process parameters of simulated solution of NpPu changing into oxides were obtained by two reduced pressure distillation methods, microwave heating method and oilbath method, and the simulated solution contains of HNO3, H2C2O4 and Zr. The oxides was gained by the method that the concentrated solution is dried and ignited. The properties of oxides were investigated by means of Xray diffraction analysis and surface analysis. The results show that the microwave heating reduced pressure distillation method can shorten concentrating time significantly than oilbath heating method, and the distilled nitric acid can be reused. The oxide obtained by microwave process has large surface area, facilitating the subsequent immobilization study more easy.