Gas exchange and chlorophyll fluorescence parameters in two ecotypes of Jatropha curcas originally growing in Hainan Province and Guizhou Province were determined by a Li-6400 portable photosynthesis analysis system (LI-6400, Li-cor USA) and a chlorophyll fluorometer (PAM 2100, Walz, Germany) in summer. The photosynthetic capacity of Jatropha curcas was high. The light saturation point (LSP) of the Hainan and Guizhou ecotypes was 1700 μmol·m-2·s-1 and 1600 μmol·m-2·s-1, and the maximum photosynthetic rate (Pmax) was 20.4 μmol m-2·s-1 and 18.9 μmol·m-2·s-1, respectively. There was no obvious difference in responses of photosynthetic rate to CO2 concentrations between the two ecotypes of Jatropha curcas, Hainan and Guizhou. The diurnal variation of net photosynthetic rate in leaves of the two ecotypes presented a two\|peak pattern. The first peak and second peak occurred at about 10:00 am and at 16:00 pm, respectively, an obvious phenomenon of “midday depression of photosynthesis”. The Pmax, LSP, LCP (light compensation point), AQY (apparent quantum yield) and Rd (dark respiration) of the Hainan ecotype were higher than those of Guizhou ecotype. The daily changes of maximal photochemical efficiency of photosystem Ⅱ (Fv/Fm) exhibited little difference between the Hainan ecotype and the Guizhou ecotype, whereas the daily changes of actual photosystem II efficiency (ΦPSⅡ) were consistent with daily changes of Pn. The Hainan ecotype displayed more tolerance to strong light intensity than Guizhou ecotype. These experimental results indicate that Jatropha curcas is a woody plant with a high photosynthetic capacity and a strong capacity for acclimation to high light intensity and, therefore, a potentially significant bioenergy source.