Abstract: The prediction approaching method proposed in the paper can attain higher accuracy in conversion on using a table of a smaller scale. An approximate conversion model between RGB and L *a *b *, and a RGB→L *a *b * table with a special structure are first set up, based on a set of measured data. Then a set of approximate RGB values are found from the table using the given L *a *b * as entries. The corresponding color difference is calculated, and is in turn used by the model to predict how the RGB values should be modified. This process is repeated until the color difference is less than a predetermined threshold value. Experiments have shown that in most cases the final RGB values capable of producing a color difference of 2～3 CIELAB units can be obtained with only 2～3 modifications.