The invention discloses polymer electrolyte which is characterized by comprising a mixture A, an organic solvent B, an I2/KI redox couple with the mole ratio of 1: 5-1: 10, a crosslinking agent and a plasticizer, wherein the mixture A comprises polyoxyethylene and a vinylidene fluoride-hexafluoropropylene copolymer according to the weight ratio of 1: 4-4: 1; the organic solvent B comprises propylene carbonate and glycol dimethyl ether according to the volume ratio of 1: 8-8: 1; the weight of the crosslinking agent is 25-125 percent of the total weight of the mixture A; the crosslinking agent is an aprotic solvent solution of thiocarbamide with the concentration of 0.05g/ml-0.10g/ml. According to the polymer electrolyte, under the synergistic effect of the plasticizer and the crosslinking agent, the ionic conductivity of the electrolyte can be effectively improved, so that a short circuit of a dye-sensitized nanocrystalline solar cell is enhanced, and a protection layer is formed by a photo-anode titanium dioxide ligand; therefore, the reaction proportion of dark reaction is reduced, open circuit voltage is increased, and the photoelectric conversion efficiency of the cell is finally improved.