The invention discloses a sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery. The positive electrode material has a core-shell structure, whereinthecomposition of the core is NaxFeyM1-yO2, the composition of the shell is NazMnO2; 0.6 < x < = 1, 0.5 < = y < 1, and 0.44 < = z < 1; M is one or more of Mn, Ni, Ti, Cu, Sn, Mg, Co, V, Cr and Nd. The preparation method of the positive electrode material is simple in process, and the prepared positive electrode material has the advantages of being low in price, high in safety, low in battery manufacturing environment requirement and the like, and can be applied to preparation of sodium ion batteries. The shell material and the core material can generate an ingenious mutual synergistic effect, so the charge-discharge specific capacity of the positive electrode material, the cycle performance and the rate capability of the battery are improved, and particularly, the cycle stability of the battery has outstanding advantages.