Abstract: Three varieties of Bougainvillea spectabilis 'Jinxinshuangse', 'lvyeyinghua' and 'Tonganhong' commonly used in the greening of Shenzhen overpass were used as testing materials to study the suitable moisture management cycle, and the effects of drought on photosynthetic characteristics were analyzed.The findings indicates that 'Tonganhong' had the highest net photosynthetic efficiency and stronger photosynthetic capacity on the 3^rd day of drought.the net photosynthetic efficiency decreased but not significantly on the 6^th day of drought.After that, the net photosynthetic rate and transpiration rate decreased significantly, indicates that the photosynthesis of 'Tonganhong' was greatly affected in the later stage of drought.'Tonganhong' has stronger drought resistance than that of 'Jinxinshuangse' and 'lvyeyinghua' based on the index.It is suggested that watering period of 'Tonganhong' should be extended appropriately in the greening of overpasses.