Using normal-leaf pepper A124 as the control and the leaf-curling mutant D26 as the test material, three light intensity treatments were applied: low light ((25±5) μmol/(m2?s)), moderate light ((200±5) μmol/(m2?s)), and high light ((500±5) μmol/(m2?s)). After 15 days of continuous treatment, leaf-curling index, biomass, chlorophyll content, gas exchange parameters, and chlorophyll fluorescence parameters were measured. In addition, paraffin sectioning was employed to observe changes in leaf cellular structure. The growth characteristics and photosynthetic physiological traits of the leaf-curling mutant D26 under different light intensities were systematically analyzed. The results showed that light intensity significantly affected pepper leaf morphology. Under low light, D26 leaves remained flat, whereas under medium and high light intensities, the leaves rolled up, with leaf-curling indices of 19.63% and 43.89%, respectively. For both accessions, total biomass decreased sequentially under medium, high, and low light conditions. Compared with A124, D26 had stronger biomass accumulation capacity and better adaptability under low light. Medium light induced leaf curling in D26 but did not affect its biomass accumulation, while high light significantly reduced leaf biomass in D26. Under high light, changes in the morphology and arrangement of leaf cells in D26 led to leaf curling. Under low light, the leaves became thinner and had a looser structure. Under different light intensities, the chlorophyll content of D26 was higher than that of A124. D26 enhanced light capture by accumulating chlorophyll under low light, showed a large decrease in chlorophyll content under medium light, and exhibited significantly reduced chlorophyll content under high light. Under low light, the photosynthetic rates of D26 and A124 were similar. Under medium and high light, stomatal conductance and transpiration rate of D26 decreased, leading to a reduction in photosynthetic rate. D26 maintained good photosynthetic efficiency under low light. Although the activity of its PSⅡ reaction center was lower under medium and high light, D26 could initiate photoprotection through a higher NPQ level to adapt to high light stress.