Suburban areas connect the city and the natural land. This kind of area is subject to high ecological sensitivity. To give full play to the ecological value of spontaneous plants, it was applied to the construction of suburban parks. We need to explore the influence factors of park characteristics on spontaneous plants. This study takes Jiangyangfan Ecological Park as the main research object. We have investigated the spontaneous plants in it and the surrounding parks. Hence, 16 kinds of park environmental characteristic factors were selected to explore their effects on the composition and diversity of spontaneous plants. The results showed that: (1) There were 138 species of spontaneous plants belonging to 126 genera and 62 families in Jiangyangfan Ecological Park. Native plants accounted for 88.10%. (2) The Shannon-Wiener diversity index of spontaneous plants was ranked as Jiangyangfan Ecological Park > White Pagoda Park > Eight Diagrams Field Relic Park > Haiyue Waterscape Park. (3) Among the overall characteristic factors, the park perimeter and the actual accessible area had the most significant positive correlation to the diversity of spontaneous plants (p < 0.05). Among the environmental element characteristic factors, the Shannon-Wiener diversity index of cultivated plants had the strongest positive correlation with the diversity of spontaneous plants (p < 0.01). The number of water bodies presented the strongest negative correlation (p < 0.01). This study provides a useful reference for the rational planning of parks in suburban areas and the construction of sustainable urban and rural landscapes. The research results will contribute to the restoration of the ecological environment.