Abstract: Four commonly appliedmathematical models were used to fit the photosynthesis-lightresponses of various sweetpotato plants under light exposures.The light saturation point (I_sat) obtained from either the rectangular or the non-rectangular hyperbolic model was considerably lower than themeasured values. Although theexponential function model predicted I_sat and the maximum net photosynthetic rate (Pn_max), it tended to give much lower valuesthan actualmeasurements on the light compensation point and the dark respiration rate. The modified rectangular hyperbolic model seemed to better fit for the functions. Using the new model, it was found that Fushu 2 and Guangshu 87 had the best photosynthetic capability among the 8 varieties of sweetpotato tested.