The relationship between bilayer nanostructure, defect density and dye-sensitized solar cell (DSCC) performances was investigated. By adjusting bilayer nanostructures, defect density of ZnO nanodendrite-nanorods structure was decreased comparing to that of nanoflower-nanorods structure. The performances of DSCC based on ZnO nanodendrites-nanorods structure and nanoflower-nanorods structure were studied by Raman spectrum, room temperature photoluminescence, dye loading, photocurrent density-voltage characteristic and open-circuit voltage decay (OCVD) technique. The device with nanodendrite-nanorods structure has lower charge recombination rate and prolonged electron lifetime due to its microstructure feature.