Temperature and water are two important environmental factors that influence flavonoid synthesis in ginkgo (Ginkgo biloba) leaves.In this paper,we studied three temperature levels (T₁,5 ℃～15 ℃;T₂,15 ℃～25 ℃;and T₃,25 ℃～35 ℃,respectively) and three soil water content levels (30%～35%,40%～45% and 55%～60% of field water capacity,respectively) on flavonoid content and activities of L-phenylalnine ammonialyase (PAL),cinnamic acid 4-hydroxylase (C4H),and 4-coumarate-CoA ligase (4CL).Results showed that:(1)A significant difference for PAL,C4H,4CL and flavonoid was found in ginkgo leaves under the temperature and water stress (P＜0.05).These three enzyme activities increased with the stress.However,the results were still different in leaves for each enzyme activity.(2)High temperature (T₃) and low temperature (T₁) increased PAL,and the T₁ only increased C4H.For 4CL,in 14 and 28 day,water was the main factor to affect 4CL,but 42 day later,the temperature became the main factor.(3)The flavonoid in ginkgo leaves was decreased with stress (P＜0.05).Same as 4CL,water was the main factor in early days,but temperature was the main factor in later days.(4)From the analysis of relationship,PAL,C4H,4CL and ginkgo leaves biomass were negatively correlated with the flavonoid content.Although the temperature and water increased these enzyme activities,the flavonoid content in ginkgo leaves still decreased.