Abstract: In order to study the carbon sequestration and oxygen release capacity, as well as the cooling and humidifying effect capacity of 20 typical urban greening tree species in Jiangsu Province, China, a portable photosynthesis meter was used to measure the key photosynthetic physiological indices such as the net photosynthetic rate and transpiration rate of each tree species in 2024.Based on the measured data, the ecological function parameters such as the amount of carbon sequestration and oxygen release, the amount of cooling and humidifying, and the water use efficiency were calculated.The results showed that the diurnal dynamic change patterns of photosynthesis and transpiration of the 20 urban greening tree species could be divided into two types: unimodal curve and bimodal curve.In terms of the amount of carbon fixation and oxygen release per unit leaf area and per unit land area, among the arbors, Liriodendron × sinoamericanum had the highest value; among the small arbors, Prunus persica 'Duplex' had the highest value; among the shrubs, Gardenia jasminoides var.radicans and Fatshedera lizei had the highest values.In terms of the amount of temperature reduction and humidity increase per unit leaf area and per unit land area, among the arbors, Zelkova serrata and Liriodendron × sinoamericanum had the highest values; among the small arbors, Prunus persica 'Duplex' had the highest value; among the shrubs, Gardenia jasminoides var.radicans and Hypericum monogynum had the highest values.Overall, among the arbors, Zelkova serrata and Liriodendron × sinoamericanum;among the small arbors, Prunus persica 'Duplex' and Prunus serrulata var.lannesiana;and among the shrubs, Gardenia jasminoides var.radicans,Ligustrum × vicaryi,Pittosporum tobira,and Fatshedera lizei:these seven tree species have relatively strong comprehensive functions in terms of carbon fixation and oxygen release capacity, alleviating the urban heat island effect, and water use efficiency.