A method improves color of projected images using a projector. The method calculates a first improvement factor, a second improvement factor and a third improvement factor, divides an original image into a red picture, a green picture and a blue picture. The method multiplies a pixel value of each pixel point of the red picture by the first improvement factor to obtain an improved red picture, multiplies a pixel value of each pixel point of the green picture by the second improvement factor to obtain an improved green picture, and multiplies a pixel value of each pixel point of the red picture by the third improvement factor to obtain an improved blue picture. The method combines the improved red, green and blue pictures to generate a combined image, and projects the combined image on a projection area to obtain the projected image having similar color to the original image.