A method of making a filter adjusts the bottom heights of the color-resisting colors to make the top ends of the color-resisting blocks be in a same level by disposing the foundation layer between the transparent substrate and the light-shielding layer and disposing the groove in the foundation layer, so that ensuring that surfaces of the filter have a good evenness and the alignment of liquid crystals is normal for enhancing the displaying effect of the liquid crystal display. The present invention improves the bottom evenness of the through holes by disposing the foundation layer on the bottoms of the through holes, thereby eliminating the “ox horn-shaped segment difference” of the protruding edges of the color-resisting blocks formed later.