The invention discloses a flexible dye-sensitized solar battery with stainless steel as the substrate and a preparation method thereof. The battery adopts seven-layer composite structure which comprises a flexible stainless steel substrate layer, an insulation film layer, a titanium film layer, a titanium dioxide natural layer, a titanium dioxide nano tube array layer, an electrolyte layer and a flexible counter electrode which are arranged in sequence from the bottom layer to the top layer, and dye molecules are embedded into the titanium dioxide nano tube of the titanium dioxide nano tube array layer. The insulation film layer is prepared on the flexible stainless steel substrate layer, then, the titanium film layer is prepared on the surface of the insulation film layer, and a stainless steel flexible photo-anode with the stainless steel substrate layer/insulation film layer/Ti film layer/TiO2 natural layer/TiO2 nano tube array layer can be obtained through anodic oxidation in water-base or organic electrolyte; after the heat treatment, dye sensitization is performed to the obtained stainless steel flexible photo-anode and electrolyte is dripped into the photo-anode, and after encapsulation, the flexible dye-sensitized solar battery with stainless steel as the substrate is obtained. The invention has the advantages of simpler preparation technique, high battery conversion efficiency and low cost.