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In order to more accurately analyze the influences of ultra high performance concrete-normal concrete (UHPC-NC) interface features on bonding strength, this paper quantitatively characterized the three-dimensional feature information of the substrate surface based on digital image technology, and studied the influences of different substrate surface roughness and coarse aggregate area on the interface bonding strength. The results indicate that there is a strong correlation between the substrate surface roughness and the area of coarse aggregate, and the correlation coefficients between the contour arithmetic mean deviation Ra and standard deviation Std of the obtained profiles and the coarse aggregate area Sc are 0.838 and 0.855, respectively. The substrate surface roughness increases with the increase of coarse aggregate area. The failure load of the interface group specimen treated with high-pressure water jet on the substrate surface increases by 143.0% to 240.0% compared to the smooth interface group specimen, while the high-pressure water jetting treatment interface group specimen could obtain 53.4% to 89.6% of the overall specimen failure load. The surface characteristics of NC substrate are key factors affecting the interface bonding strength. The characteristic parameters of the substrate surface roughness, the profile arithmetic mean deviation Ra, standard deviation Std and coarse aggregate area Sc, are positively correlated with the interface bonding strength, and their correlation coefficients are 0.935, 0.927 and 0.959, respectively. The interface bonding strength increases with the increase of substrate surface roughness and coarse aggregate area. [ABSTRACT FROM AUTHOR]