The utility model relates to a color mixing device used for color enlarge-printing, which comprises a light mixing tube, a casing, a bulb and color filter components; wherein, only one bulb is used, the color filter components comprise a red, a green and a blue color filter, which are spliced together. The color filter components are fixed onto the brackets, which are driven by two electromotors able to move in line with the horizontal and vertical coordinates. Under the control of the numerical control device, the photic proportion of the three color filters can be adjusted in line with the designated chrominance to complete the process of mixing colors. The utility model has the advantage of employing fewer bulbs, low energy consumption and waste, simple structure, time saving, high efficiency and excellent color enlarge-printing.