Abstract: Respiration rate in light (Rd) and the CO2 compensation point in absence of Rd (г*） were 0.33μmol·m-2·s-1 and 46.5μl·L-1 in leaves of Musa paradisiaca exposed to UVB radiation (4.8μW·cm-2) respectivty. They were higher than those in control plants by 5.6% and 10%, respectively. The initial slope of lightresponse curves, the apparent quantum yield (αA) in leaves of control plants was 0.023±0.007 while the relative value was decreased by 13.0% in plants exposed to UVB radiation. A parameter related to the efficiency of light energy conversion (δ) was also decreased by 28.6% for plants exposed to UVB radiation in comparison with that of control plant. The partial An/Ci curves measured under θp 1100μmol·m-2·s-1, was An=0.028Ci+1.41 for leaves of control plants and An=0.021Ci+1.01 for leaves exposed to UVB radiation. Maximum carboxylation rate (Vcmax) and electron transport rate in saturated θp in leaves exposed to UVB treatment were also lower than those of controls considerably. The partitioning coefficients for leaf nitrogen in Rubisco (PR) and in bioenergetic (PB) in leaves exposed to UVB radiation were lower than those of controls by 8.1% and 3.0%, respectively. And the fraction of leaf nitrogen in thylakoid lightharvesting component (PL) increased finely in plant exposed to UVB radiation as compared to that of controls. The results imply that supplementary UV-B radiation cause the decrease of nitrogen partition in the components of photosynthetic carbon cycle and decrease photosynthetic rate.