The invention discloses a co-doped flexible sodium ion battery cathode material and a preparation method thereof. The co-doped flexible sodium ion battery cathode material has the chemical formula ofNa2NimMnFe (CN) 6; Wherein M is at least one of Mn, Co, Ti, Fe, Cu, Zn and Cr; 0 <= m <= 1, 0 <= n <= 1. At that same time, the preparation method of the co-doped flexible sodium ion battery cathode material is also disclosed. The flexible composite electrode material obtained by the invention has the advantages of high capacity, high cycle stability and the like of electrochemical performance, meanwhile, has excellent flexibility and mechanical tensile strength, and the preparation process is very simple, low in cost, environmentally friendly and pollution-free, is suitable for mass preparation, and has excellent market application value.