The invention discloses a method for assembling a color wheel. The color wheel comprises a substrate, a color layer and an optical modification layer which are sequentially superposed, wherein the color layer is formed by splicing at least two color sections along respective splicing side edges; the at least two color sections are at least two wavelength conversion sheets or at least one wavelength conversion sheet and a diffusion sheet; and the optical modification layer is formed by splicing at least two optical membranes which are used for modifying color light emitted from a correspondingcolor section respectively along respective splicing side edges. The assembly method comprises the following steps of: fixing each color section on a corresponding optical membrane to ensure that thesplicing side edges of all the color sections are flush with the splicing side edges of the optical membranes corresponding to the color sections; placing all the optical membranes fixedly provided with the color sections on the substrate sequentially, and splicing the optical membranes together along the splicing side edges to ensure that the color sections are positioned between the optical membranes corresponding to the color sections and the substrate; and fixing all the optical membranes and the substrate. By the method, the assembly efficiency of the color wheel can be greatly improved.