Abstract: The effects of four precursors on flavonoids biosynthesis in cell suspension cultures of Glycyrrhiza inflata Bat.were studied.The results showed that all of these precursors with the appropriate concentrations not only affected the cell growth,but also promoted the flavonoids biosynthesis.Moreover,the flavonoids productions were all beyond 100 mg/L when the best addition concentrations of phenylalanine,tyrosine,cinnamic acid and NaOAc were 20,5,5 and 5 mg/L,respectively.The optimum time for tyrosine addition was the 5th day during the cell culture,while it was the 10th day for the other three kinds of precursors.Among the four precursors,tyrosine was the most effective in which the maximum flavonoids production reached 113.0 mg/L,1.43 times as that of the control.Additionally,the addition of phenylalanine and NaOAc enhanced the activity of phenylalanine ammonialyase,one of the key enzymes of the flavonoids biosynthesis,while the addition of cinnamic acid deduced it.