Abstract□□Ambient illumination and background color saturation are two major factors in visual performance, they have great influence on the speed of reading, the accuracy rate of cognition, even the individual’s emotion, and all of this may affect the visual performance. Thus, the interaction effect of ambient illumination conditions and background color saturation on visual performance with LCD screens is investigated in this study. The experiment evaluate three independent variables: illumination color, illumination intensity and background color saturation. Illumination color had three levels: 2700k, 4000k and 6500k, and illumination intensity had two levels: 250lux and 750lux. Five background color saturation were employed in the experiment. Sixty participants were randomly assigned to each of the six treatments of the between-subjects factor, with 10 participants for each treatment. Every subject completed the five levels of the within-subject factor. Two dependent measures: the percentage of correctly identified letters, and the speed of cognitive process. Subjects begin the test only after reading the experimental instructions. At the beginning of each trial subjects were asked to fixate on the center of the screen where symbol “+”. Three second later, a stimulus which consists of four capital letters was presented in the center area of the screen for 200ms. The subjects were required to write down as many letters as they can identify in the corresponding position. Results of the experiment indicate that the all the independent variables had significant effect on the speed, but only the illumination color had significant effect on the percentage of correctly identified letters. The illumination intensity × background color saturation interaction was significant on the speed, The interaction of all the three independent variables had significant effect on the percentage of correctly identified letters, but no significant effect on the speed。 In conclusion, the interaction effect of ambient illumination conditions and background color saturation has different influence on visual performance with LCD screens, and visual performance can be improved by adjusting the background color saturation under the different ambient illumination condition. With respect to 250lux, the value of the saturation should change in the range of 102 -153, and with respect to 750lux×2700k, in order to improve the percentage of correctly identified letters, the value of saturation should change in the range of 153 -204.