A model for predicting spectral reflectance of gravure spot color scales is proposed based on the relationship between density and spectral reflectance. Firstly, this method establishes the relationship between the solid spectral reflectance and its density according to the definition of density, and establishes the calculation method of the tone spectral reflectance based on the solid spectral reflectance. Then, according to the superposition principle of density, assuming that the proportional relationship between tone density and solid density is established, the relationship between tone density solid density and substrate density is established. Finally, combined with calculating the tone spectral reflectance, a spectral reflectance prediction model of the gravure spot color scale is established. Thirty kinds of spot color inks are mixed and used to print samples by gravure printing. The prediction model is verified by the coefficient of determination R2 and the color difference. The experimental results show that the proportional coefficients of the actual tone density and the actual solid density are the same under the same dot area rate of different spot colors, and the determination coefficients R2 of both are greater than 0.98. Based on this relationship, the prediction model established in this paper has a high determination coefficient at different dot area rates, the root mean square error is less than 0.01, and the maximum color difference is 2.667 NBS. Finally, another ten different spot color inks are prepared to print simples under the same process conditions, and the proportion coefficient between the actual tone density and the actual solid density is used to verify the accuracy of the model in predicting the tone spectral reflectance of spot color ink by color difference formula. The color difference results show that 82.12% of the color difference is less than 2.5 NBS, most of the color difference is between 0.5～2 NBS, accounting for 58.32% of the total frequency, and the average color difference is 1.58 NBS, which meets the requirements of enterprises for fine reproduction of colors. It is verified that the model has high accuracy for predicting the spectral reflectance of the gravure spot color scale, and it can provide a scientific method for digital proofing instead of gravure machine proofing.