Objective Objective To analyze and study the effect of the image noise when evaluating the print mottle. Methods The denoising assessment model of print model was proposed based on the assessment model of image grayscale change in print mottle and wavelet denoising. The back trap mottle on the newspaper was then taken as an example, correlation analysis was performed between the print mottle index of modeling before and after denoising and the visual evaluation. Results The correlation factor with visual evaluation was largely improved when the noise on the image of print mottle was deceased. The correlation coefficient was at least 0.71 after denoising of image compared with the correlation coefficient of 0.53 without denosing for this case. Conclusion The noise of image has a key impact on the evaluation of print mottle, which should be considered when analyzing and assessing print mottle.