The invention relates to the technical field of sodium ion batteries, in particular to a positive electrode material precursor, a preparation method thereof and a positive electrode material.The preparation method comprises the following steps that S1, an iron source, a copper source and a first complexing agent are mixed and subjected to a complexing reaction, and a mixed solution is obtained; s2, a reducing agent, a second complexing agent and water are mixed to obtain a base solution, a manganese source, a nickel source, the mixed solution and an alkaline solution are added into the base solution for precipitation reaction, and the positive electrode material precursor is obtained.By means of the method, the four elements of manganese, iron, nickel and copper can be evenly distributed in an atomic scale, the synergistic effect of manganese, iron, nickel and copper is fully exerted, and the positive electrode material is obtained. And the specific capacity of the positive electrode material formed by the precursor is remarkably improved by controlling the molar ratio of four elements of manganese, iron, nickel and copper in the molecular formula.