The present invention relates to a coating composition having excellent wavelength conversion efficiency and a wavelength converting thin film/sheet prepared using the same. The coating composition of the present disclosure includes 1 to 60 wt % of polyorgano-silsesquioxane, 0.0001 to 30.0 wt % of a wavelength converting agent, and a solvent, and exhibits a transmittance of 70% or more as compared to that of an aqueous solution. A wavelength converting thin film/sheet prepared by using the coating composition has not only excellent photoluminescence, thermal resistance, and light-fastness, but also moisture and oxygen permeability is low, and the visible light transmittance thereof is 70% or more as compared to that of the air, and when patterning is added, the photoluminescence intensity of sheet is at least two-fold higher than that of a non-patterned sheet. Therefore, the coating composition of the present invention may be conveniently used in the preparation of a wavelength converting thin film/sheet, and feasibly applied to the preparation of a solar cell in an efficient manner.