Abstract: One year old seedlings of Ginkgo (Ginkgo biloba L.) were grown in a pot under greenhouse conditions with varying soil water levels to determine photosynthetic characteristics. There were 16 different treatments, including 4 water levels (80%, 60%, 40% and 20～//00 of field capacity) and 4 varieties of Ginkgo, and the time of treatment was 100 days. The results were as follows: (1) There was little variation in the net photosynthetic rate, stomatal conductance,intercellular CO2 concentration, transpiration rate and Fv/Fm at the water condition of 80% and 60% of field capacity, but the 5 indexes decreased obviously at the water condition of 40% and 20% of field capacity; (2) The correlation coefficients between 5 indexes were all high, and the correlation coefficients between net photosynthetic rate and intercellular CO2 concentration was 0. 951, and the correlation coefficients between Fv/Fm and net photosynthetic rate was 0. 912; (3)The decreasing of net photosynthetic rate of Ginkgo under water stress was caused by stomatal limitation, and the electronic transmitting and COz assimilating also were restrained under water stress.