Abstract: The effects of different phosphate levels on the photosynthesis of satsuma mandarin(Citrus unshiu Marc ) leaves were studied in the culture solution It shows that under the lack of phosphate, phosphate content, Rubisco activity, rate of RuBP regeneration, apparent quantum yield (AQY), photochemical efficiency of PSⅡ(Fv/Fm)and electron transport rate (ETR) decrease, in addition, the ratio of photorespiratory rate (Pr) to net photosynthetic rate (Pn) go up; PSⅡ reaction centers is reversible inactivation; chlorophyll content change unsignally After supplying leaves being lack of phosphate with 20 mmol/L KH2PO4 for 12 hours, the Pn, rubisco activity, rate of RuBP regeneration, AQY, photochemical efficiency of PSⅡ, PSⅡ reaction centers activity and ETR come back rapidly, and the Pr/Pn decrease The Pn, rubisco activity and rate of RuBP regeneration declined, while phosphorus content increased in the surplus phosphate, but the chlorophyll content, Pr, AQY, chlorophyll fluorescence parameters Fo, Fv/Fm, and the ETR keep the stabilization basically