The aim of this work was to study the effect of fluorescent paper substrate on the reflectance of recto-verso halftone print. Based on the assumption that the reflectance of the ink and the paper is the same, considering that the fluorescent substrate can absorb the invisible ultraviolet light and emit the visible light influencing the overall reflectance, the impact of fluorescent substrate is equivalent to changes in the upward and downward reflectance of the paper substrate, as well as the recto and verso image transmittance of the ink. Meanwhile, the dot gain was taken into account, and the theory of distance classification Clapper-Yule model was used for analysis. Through numerical simulation, the old and the new models were compared, and the reasonability and accuracy of the new model were verified. As a result, a Clapper-Yule front reflectance model was established for recto-verso halftone image printed on fluorescent paper substrate. In conclusion, the effect of fluorescent paper substrate must be included in reflectance forecasting of Clapper-Yule model.