Abstract: To provide quantitative analysis for plant allocation, leaf economic spectrum theory was used as the starting point to study the response mechanism of leaf functional traits of urban park plants to thermal environmental gradient. Firstly, based on land surface temperature inversion map and measured environmental data, Suzhou urban area was divided into three different gradients: hightemperature region（HTR）, medium-temperature region（MTR） s and low-temperature region（CTR）. Six common tree species as Osmanthus fragrans, Camphora officinarum, Photinia serratifolia, Ginkgo biloba, Acer palmatum and Prunus serrulata were selected from the parks in different gradient zones.Those plants were studied to determine the leaf functional traits, and the response mechanism of the traits to different temperature gradients was analyzed by statistical methods. The results showed that（1） Compared with other gradients, park plants in high temperature areas often showed high leaf dry matter content（LDMC）, low specific leaf area（SLA）, low chlorophyll value（SPAD）, low photosynthetic rate（Pn） and leaf nitrogen content per unit mass(N_mass), and relatively high stomatal density, small stomatal size and stomatal aperture.（2） There was a consistent correlation among leaf functional traits of the six park plants with different thermal environmental gradients. Leaf dry matter content was negatively correlated with specific leaf area, and significantly positively correlated with stomatal density（SD） and stomatal size（SS）, while specific leaf area was significantly positively correlated with leaf nitrogen content per unit mass. Stomatal conductance（Gs） was positively correlated with photosynthetic rate and transpiration rate（Tr）.（3） Redundancy analysis showed that stomatal density, stomatal conductance and photosynthetic rate were positively correlated with land surface temperature. Leaf area, leaf dry matter content, leaf fresh weight, stomatal stomatal aperture（SA）, stomatal size, leaf nitrogen per unit mass, leaf carbon(C_mass) content and photosynthetic rate were positively correlated with soil water content.（4） The fuzzy membership function analysis showed that Camphora officinarum and Osmanthus fragrans had good adaptability under heat stress, while maple, cherry blossom and ginkgo had weak adaptability.