Abstract: An experiment was conducted in a plastic greenhouse to assess fruit setting rate and major photosynthetic and chlorophyll characteristics of purple and green chili pepper varieties in summer. For self fruit setting studies，18 and 21 purple and green varieties，respectively were hand pollinated at blossom bud stage. Similarly，10 purple and 9 green chili peppers were randomly selected for reciprocal hybridization to evaluate cross fruit setting rate. Main parameters of photosynthesis and chlorophyll fluorescence were measured from 5 varieties of chili pepper with diverse leaf colours，green 7035，high purple 7033，medium purple 7037，slight purple 7034（with purple veins），and slight purple 7039 (with green veins)to assess the pigment content. The following results were obtained：（1）significantly higher fruit self-setting rate of purple（72.19%）than the green chili peppers（37.12%），significantly higher fruit cross-setting rate was recorded. The fruit cross setting rate was 55.99 and 21.60% when purple and green chili pepper varieties were used as female parents respectively. （2）the amount anthocyanin（An）and ratio of chlorophyll a and b（Chl. a/b）were significantly higher in leaves of purple chili than the green ones，amount Chl. a and carotenoid（Car）were also higher in most purple chili peppers，but insignificantly in amount Chl. b. （3）transpiration rate（Tr），stomatal conductance（Gs）and net photosynthetic rate（Pn）of purple and green chili pepper showed a similar trend of double peak curve. Light compensation point（LCP），light saturation point（LSP）and actual Pn during the day time of high temperatures were significantly higher while apparent quantum efficiency（AQY）were lower in all purple varieties than the green ones. （4）purple chili pepper could prevent excessive absorption of solar energy by pigment antennas besides by partly reversible inactivation of the reaction center（RC）of photosystem Ⅱ（PSⅡ）to reduce the harm of excess energy absorbed，the only strategy found in green pepper. The energy of dissipation（DIo/CS） as well as absorption（ABS/CS），capture（TRo/CS）and delivery（ETo/CS）in purple varieties 7033 and 7034 was lower，while the maximum of fluorescence（Fm），maximum of photochemical efficiency（Fv/Fm），potential photochemical efficiency（Fv/Fo）and electron transport efficiency（ETo/TRo）were higher than the green pepper.

Key words: chili pepper, purple, pigment, fruit setting rate, photosynthesis, chlorophyll fluorescence