Abstract: Due to the importance of ornamental trees in urban ecosystem, it is crucial to investigate and understand the distribution, prevalence, and intensity of semi-parasitic plants (Loranthaceae and Viscum spp.) of garden trees and study the influencing factors. A survey of semi-parasitic plants in Lidui Park, Dujiangyan City, Sichuan Province, showed that out of 1,362 woody plants, 171 individuals belonging to 30 species, 30 genera, and 21 families were served as the host plants of mistletoe, resulting in an overall parasitism rate of 12.8%. A total of 490 mistletoe clusters were recorded, with an average infestation intensity of 2.8 clusters per host. Parasitic plants were predominantly found in open areas adjacent to water bodies and low-rise buildings. The tree species with the highest parasitism rate and host preference were Pyrus betulaefolia, Gleditsia sinensis, Broussonetia papyrifera, Salix babylonica, Pterocarya stenoptera, and Metasequoia glyptostroboides. Five variables (leaf habit, height, DBH, adjacent to water body, adjacent to building construction) were positively correlated with the parasitism rate. One variable (edible for birds) was negatively correlated with the parasitism rate. Another three variables (height, leaf habit, edible for birds) had a significant positive impact on the parasitism intensity. It is recommend that the semi-parasitic plants on the ancient trees in Lidui Park should be removed in a targeted manner, and further research on the impact of semi-parasitci plants should be carried out to maintain the biodiversity of Lidui Park.