Residential green spaces, as part of the urban ecosystem, serve as the primary means for daily encounters with nature. It provides residents with close-up service value, enhancing their well-being. Current biodiversity research predominantly emphasizes macro-scale analyses, frequently neglecting micro-scale perspectives, particularly individual perceptions and evaluations in residential contexts. This study addresses this gap by focusing on the neighborhood scale, surveying plant diversity (including cultivated and spontaneous plants) in 30 old residential communities within the core area of Chengdu"s urban center (inside the Third Ring Road), and assessing the measured levels of plant diversity. Using the willingness to pay method, the study evaluates the value of plant diversity and explores the relationship between diversity levels and their value. Furthermore, multiple linear regression is employed to analyze the factors that influencing residents" valuation of plant diversity within these communities. The results indicate that: (1) 275 1m x 1m quadrats were established, recording 475 species belonging to 126 families and 341 genera of plants. The overall plant diversity in the community ranges from 37 to 122 species, with the ratio of cultivated to spontaneous plant diversity being 1:1.5. This indicates that spontaneous plants constitute a significant component of plant diversity in residential green spaces. (2) Regarding protecting/maintaining plant diversity within residential communities, the residents" willingness to pay ranges from 127.79 to 3659.89 CNY (M ± SD = 881.71±793.62 CNY), showing considerable variation in the perceived value of plant diversity among communities. (3) The overall and cultivated plant diversity in residential communities significantly correlates with residents" willingness to pay. However, there is no correlation between spontaneous plant diversity and residents" willingness to pay. This indicates that cultivated plants are the primary focus for residents when evaluating the value of plant diversity. In contrast, the widely present diversity of spontaneous plants and their value may not be widely recognized by residents. (4) Among the socioeconomic factors, residents" age and education level have a significant negative impact on the valuation of plant diversity. Specifically, older residents and those with higher education tend to be less willing to pay. Grounded in human preferences and needs, this study quantitatively explores the relationship between plant diversity levels and residents" valuation of them. It highlights the disparity between residents" strong emphasis on cultivated plants and their limited awareness of the contributions made by spontaneous plants, underscoring the urgent need to enhance public awareness and understanding in this area. The findings provide a scientific basis for achieving low-cost, sustainable urban ecological landscapes.