Abstract: An optimized uniform colour appearance space named UCAS is deduced based on the revised edition of colour appearance model CIECAM97s according to BFD, RIT DuPont, Witt1999 and Leeds colour difference evaluation data sets. Tested by a synthetically statistical index P ′ F/3 with the introduction of an optimized lightness correcting factor, the results show that the uniformity of UCAS is close to the new German standard DIN99 issued in 1999 and better than CIELAB recommended by CIE in 1976.