Aiming at the problems of low accuracy and unstable results of the spectrophotometer based on Lambert-Beer law in measuring dye concentration in high concentration and dark color dye solution, a soft sensor model is presented. The monochromatic light is regarded as light quantum, the dye molecule is regarded as a one-dimensional harmonic oscillator barrier, Schrödinger equation is used to solve the transmission of light quantum in tunneling penetrating through dye solution, and a mathematical model of the relationship among absorbance, dye concentration and the wavelength of the tested light is obtained. Furthermore, the model is simplified in the range of 400~700 nm of testing wavelength and a soft sensor model of dye solution concentration versus absorbance is obtained from the maximum absorbance and corresponding wavelength. The least square method is used to determine the model coefficients of a certain dye, at last, measuring dye concentration from maximum absorbance is achieved. In this paper, the soft sensor model of single-component dye concentration based on optical quantum tunneling penetration explains the selective absorption of Lambert-Beer law from the microscopic interaction between optical quantum and dye molecules. The model has a good effect on the concentration prediction of deep color and high concentration dye solution, expands the dye solution concentration measurement range of spectrophotometer, and improves the measurement accuracy.