Abstract: La_1-xNa_xMnO_2.825（x=0.05,0.10,0.15,0.20） system with oxygen deficiency was prepared by the solid-state reaction method with high-temperature sintering.XRD patterns,infrared spectra,Raman spectra,M-T curves,ESR curves and ρ-T curves of the samples were measured.The experimental results show that compared with La_1-xNa_xMnO₃ system,in this system,the magnetization value becomes smaller,the Curie temperature TC decreases,and the phase separation appears,because the oxygen deficiency changes the Mn³⁺/Mn⁴⁺ proportion and the oxygen concentration in the samples is inhomogeneous;the resistivity of the system increases,and most samples exhibit the insulator state,because of the competition among the lattice function,the spin function induced by the oxygen vacancy,and the double-exchange function of Mn³⁺/Mn⁴⁺.