The invention discloses an anion valence-varying layer oxide material, and a preparation method and application thereof. The chemical formula of the material is: Naa[LibMncMd]O2+[beta]; M is an element which is doped and substituted for a transition metal site; a, b, c , d and [beta] are the mole percentages of the corresponding elements respectively; the relationship between a, b, c, d and [beta]satisfies the formula: b+c+d=1, and a+b+4c+md=2(2+[beta]); 0.6<=a<=1, 0<=b<=0.4, 0.5<=c<=0.8, 0<=d<=0.3, and -0.02<=[beta]<=0.02; m is the valence state of M; and the space group of materials is P63 / mmc or R-3m, the corresponding structure is P2 phase or P3 phase, and the anion valence-varying layer oxide material is used for the positive electrode active material of sodium ion secondary battery.When charging is performed in the first week, the lattice oxygen ion is converted from a negative bivalence to a higher valence state, electrons are completely provided by the oxygen ions to achieveactivation of the material; when discharge is performed in the first week, the oxygen ions losing electrons regain electrons from the high valence state to the negative bivalence, and the manganese metal is converted from a tetravalence to a tervalence, and the charging and discharging process after two weeks has the valence varying of the oxygen ions and the valence varying of the manganese.