The paper aims to discuss visual characteristics of contrast sensitivity of different ages to get the contrast sensitivity function model. Based on the color space of LCH, 30 observers of three groups of youth (18~25 years old), middle age (30~45 years old) and old age (50~70 years old) were measured for lightness, chroma and hue angle contrast sensitivity curves. With the increase of the spatial frequency, the changes slowed slowly from low to high; the human eye was the most sensitive when the spatial frequency was 2~4 circles/degree. The lightness contrast sensitivity is higher than that of chroma and hue angle. The contrast sensitivity of the youth group is higher than the middle and old age groups. The exponential function is used to fit the measured data and a contrast sensitivity function model is established. The model can be used to realize the modeling of human visual system. It can use mathematical formulas to predict the human eye perception of the quality of color images.