Abstract: The Li-6400 portable photosynthesis system was used to study the photosynthetic characteristics of grafted eggplant on flourishing fruit in greenhouse. The result showed that the curve of photosynthetic daily variation of the upper position leaves had two peaks, with an obvious midday depression in eggplant leaf in greenhouse. The first peak occurred at about 11:30 am, the net photosynthetic rate was 10.2μmol/(m2·s), the second peak occurred at about 13:00pm, the net photosynthetic rate was 9.4μmol/(m2·s). The main reason for the midday depression of photosynthetic rate was stomatal factors. At midday, light intensity was the largest, vapor pressure deficit between leaves and air reached maximum, but air relative humidity, stomatal conductance and intercellular CO2 concentration reached minimum, occurred photosynthetic midday depression.