The research was conducted in Horqin Sandy Land to evaluate the responses of photosynthetic characteristics, chlorophyll fluorescence and dry matter accumulation of oriental lilies" Sorbonne" at water stress treatment (5-day, 10-day, 15-day, 20-day, 25-day). The results show water stress decreases net photosynthetic rate, transpiration rate, and dry matter accumulation. The decrease of net photosynthetic rate of the oriental lilies under water stress may result from stomatal and non-stomatal limitations, and the water stress induced "midday depression" phenomenon. Water stress also affected PSⅡ, and it decreased the maximum fluorescence, variable fluorescence and the maximum photochemical efficiency. Water stress, therefore, is the primary photosynthetic process limitation of the oriental lilies. Appropriate watering is recommended to improve photosynthetic efficiency and alleviate photodamage so as to increase the quality of the lilies in the Horqin Sandy Land.