Abstract: The visual preference influenced by riverbed vegetation was studied in this paper. The study area is located in the Liou River and Ma-Yuan-Tou River in Taichung city, central Taiwan. Five artificialized sections in both rivers were selected as the observation sites to examine the changes in the riverbed. The green looking ratio (GR) was used to evaluate the images of green areas in spaces due to vegetation on the riverbed. Six cognitive factors: naturalness N, vividness V, harmony H, closure CL, continuity CO, and mystery M, were used to discuss the factors associated with visual preference. First, various river landscape images with changes in riverbed vegetation were collected and simulated by image processing. Second, the visual preference and cognitive factors were rated by the questionnaire survey method. A total of 246 valid questionnaires were used. Finally, the visual preference associated with GR and the cognitive factors were analyzed. The results showed that the visual preference P increased with increasing GR, especially when GR > 40%. A higher N, V, and CO, or a lower CL can help promote visual preference.