###### Abstract  
Studies on the influence of parasitism on plants based on hyperspectral analysis have not been reported so far. To fully understand the variation characteristics and laws of leaf reflectance spectrum and functional traits after the urban plant parasitized by _Cuscuta japonica Choisy_. _Osmanthus fragrans_ (Thunb.) Lour. was taken as the research object to analyze the spectral reflectance and functional traits characteristics at different parasitized stages. Results showed that the spectral reflectance was higher than those being parasitized in the visible and near-infrared range. The spectral reflectance in 750-1400 nm was the sensitive range of spectral response of host plant to parasitic infection, which is universal at different parasitic stages. We established a chlorophyll inversion model (y = \(-\)65913.323x + 9.783, \(R^{2}\) = 0.6888) based on the reflectance of red valley, which can be used for chlorophyll content of the parasitic _Osmanthus fragrans_. There was a significant correlation between spectral parameters and chlorophyll content index. Through the change of spectral parameters, we can predict the chlorophyll content of _Osmanthus fragrans_ under different parasitic degrees. After being parasitized, the leaf functional traits of host plant were generally characterized by large leaf thickness, small leaf area, small specific leaf area, low relative chlorophyll content, high leaf dry matter content and high leaf tissue density. These findings indicate that the host plant have adopted a certain trade-off strategy to maintain their growth in the invasion environment of parasitic plants. Therefore, we suspect that the leaf economics spectrum may also exist in the parasitic environment, and there was a general trend toward the \"slow investment-return\" type in the global leaf economics spectrum. 1  
[table]plant is often covered with the stem strips of _Cuscuta japonica Choisy_, causing the host plant to grow poorly and even causing the whole host plant to die [11]. Therefore, parasitic plants are one of the important factors that harm urban greening plants and threaten the urban environment seriously. Research on _Cuscuta japonica Choisy_ parasitism mainly focuses on its own biological and ecological characteristics and its effects on photosynthetic physiology and ecosystem of parasitic objects [11; 12; 13]. For example, [PERSON] et al. study the effects of _Cuscuta japonica Choisy_ parasitism on the growth and reproduction of _Solidago canadensis_ L. [PERSON] et al. study the growth trade-off mechanism of _Alternanthera philosoreoides_ (Mart.) [PERSON]. on _Cuscuta japonica Choisy_ parasitism [14; 15]. All of these indicate that the host plants often change their growth defense strategies to maintain their own survival and reproduction after being subjected to _Cuscuta japonica Choisy_ parasitism stress. Also, many studies have shown that there are many uncertainties in the impact of parasitic plants on the biomass of the community in which they live, which are often affected by the characteristics of the communities themselves, external environment and other factors [16; 17; 18]. _Osmanthus fragrans Lour._, one of the most common tree species in China, plays an important role in the city's main ecological, cultural and landscape functions. However, the parasitism of _Cuscuta japonica Choisy_ seriously hinders the normal growth of _Osmanthus fragrans_. Health diagnosis, monitoring and early warning of urban trees have always been a hot spot in international urban forestry research. Therefore, how to monitor and obtain the growth status and the infringed status of the damaged vegetation is the key to effectively prevent and control the infringement. In recent years, with the rapid development of hyperspectral technology, it has been widely used in forestry monitoring. Hyperspectral data has the advantages of high resolution, abundant information and simple data acquisition [19; 20].