In the past ten years, smartphones have gone far beyond communication tools. The average number of apps per capita reached more than eighty, which brings difficulties to the search and recognition of icons. As the number of apps increased, app folders became widely used, which also brought up new problems, i.e., how to search and recognize the apps by their thumbnails icons. Furthermore, those icons are displayed under all kinds of personalized wallpapers. The present study focused on the recognition of thumbnail icons in the folder on wallpapers of different complexity. According to the literature, the contrast between icon and background, and complexity of the wallpaper are two key factors for icon identification. The contrast is determined by the opacity of folder and the brightness of icons. Thus, we studied the effect of the brightness of icons, the opacity of the folder, and the complexity of the wallpapers on icon selecting. Twenty-three users participated in the experiment. The results show interaction effect of wallpaper complexity and folder opacity on search performance and subjective rating. On the complex wallpaper, with the increase of the opacity of the folder background, the search time and the subjective difficulty decreased significantly, the aesthetic and clarity increased significantly. So we recommend high folder opacity for complex wallpaper. On the simple wallpaper, the search time and subjective difficulty does not change with the opacity of the folder background. The aesthetic increased between low level to medium level but decreased at a high level, which imply the folder opacity for simple wallpaper shouldn’t be too high.