The invention discloses a high-capacity P2-type positive electrode material of a sodium-ion battery, and a method for orderly improving specific capacity by inhibiting sodium / vacancy. The positive electrode material is a sodium-based layered metal oxide NaxTmO2, Tm is a transition metal, Tm comprises one or more of Mn, Fe, Ni, Co and other elements, and x is a stoichiometric number of sodium and ranges from 0.55 to 0.65. By regulating the content of sodium ions in the P2-type layered positive electrode material of the sodium ion battery, the charge order of the transition metal layer and the sodium / vacancy order in the charging and discharging process are effectively inhibited, the diffusion rate of the sodium ions in the P2-type layered positive electrode material is improved, and then the electrode material with higher specific capacity is obtained. The method disclosed by the invention is simple and easy to operate, rich in raw materials, low in price and high in practical application degree, can provide a new insight for structure and performance optimization of the layered positive electrode material of the sodium-ion battery, and has a wide application prospect.