To study a new algorithm for halftone optical dot gain based on the paper-based light scattering theory. Applying point spread function and probability methods, the light scattering and osmotic effect of halftone print were analyzed, and the exact expressions of the reflectivity of the blank part, the dot part and the halftone print were deduces. Furthermore, the dependence of the optical dot gain on the dot area coverage of the print, the ink layer spectral transmittance, and the paper-based spectral reflectivity was analyzed, and a new halftone optical dot gain algorithm model was established. Comparative verification experiments were conducted for the predicted spectral reflectivity and the measured spectral reflectivity of the print using the classical spectral Murray-Davis model and the Murray-Davis model amended using this algorithm. The Murray-Davis model amended using this algorithm gave a closer value with the measured spectral reflectivity, with a maximum chromatic aberration of max Δ E2000=1.53 and a minimum chromatic aberration of minΔE2000=0.89. For colors with ΔE2000＜2, the human eyes showed visual approximate equality. Using the classical Murray-Davis amended by the proposed model, better prediction results of spectral reflectivity were obtained, with higher accuracy.