Abstract: ObjectiveThis study was conducted to explore the response mechanism of photosynthesis to CO2 in Cin-namomum migao H. W. Li seedlings under different phosphorus levels,in order to provide reference for scientific phospho-rus application and cultivation of C. migao in southwestern China.MethodThis study took half-year C. migao seedlings as experimental material. Four phosphorus(KH2PO4)supply concentrations(CK was 1.000 mmol/L,P1,P2 and P3 were 0.125,0.500 and 2.000 mmol/L respectively)were set. Photosynthetic characteristics of the C. migao seedlings under dif-ferent treatments were determinated,and light response curves and parameters were fitted by using right angle hyperbola model,non-right angle hyperbola model and modified right angle hyperbola model(Pn/Ci).ResultDetermination coeffi-cients R2 of the three fitting models on C. migao seedlings photosynthesis response were above 0.9900,and the effective-ness trend was Pn/Ci model>non-right angle hyperbola model>right angle hyperbola model. Pn/Ci model was the most practical one for photosynthesis-CO2 response of C. migao seedlings,and fitting effectiveness of the model was in line with this trend under different phosphorus levels. Under all phosphorus treatments,except intercellular CO2 concentration (Ci),the rank of net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)was CK>P3>P2>P1, and Pn,Gs and Tr under P1 treatment were significantly different from those under other treatments(P<0.05),which showed that the photosynthetic efficiency of C. migao seedlings was the highest under 1.000 mmol/L KH2PO4 treatment.ConclusionThe Pn/Ci model is the most suitable for photosynthesis-CO2 response fitting of C. migao seedlings. Appropri-ate application of phosphorus can promote C. migao photosynthesis. The most suitable content of phosphorus in soil for C. migao seedlings is 1.000 mmol/L.