Caramel color is an important component of edible coloring. Plain caramel color has a good safety profile and therefore, has currently received a lot of research interests. The effects of thermo holding time, concentration, and heat treatment on the physicochemical properties of plain caramel color were studied. The results showed that pH of plain caramel color decreased with increasing thermo holding time, which then approached an equillibrium. The color index of plain caramel color increased first and then decreased as thermo holding time increased, and then became stable after 120 min. Both, red and yellow indices of plain caramel color decreased at first and then increased as thermo holding time increased, and stabilized after 120 min. Increase in thermo holding time caused more changes in the color, namely, red and yellow indices before and after heat treatment; however, the changes were similar after 90 min. Thermo holding procedure following the plain caramel color prepareation promoted further reactions of substances , improving stability and quality indices of plain caramel color. Concentration also affected the stability of plain caramel color, where higher concentration inhibited the transfer of substances within the caramel color, leading to higher stability.