Objective:To study the dose and time dependent hepatotoxicity and pathological change induced by Radix et Rhizoma Sophorae Tonkinensis（RRST） in mice.Method:After 14 days observation

the medial lethal dose（LD50） of RRST decoction with oral administration in mice was calculated.In addition

the liver weight /body weight index was measured

and pathological change of liver under microscope was observed.Result:The LD50 value of RRST of batch A（No.081012） was 31.935 g（crude drug） /kg

with the 95% confidence level between 30.509 ～ 33.506 g（crude drug）.kg-1;that of batch B（No.0904295） was 16.39 g（crude drug）.kg-1

with the 95% confidence level between 14.426 ～ 18.38 g（crude drug）.kg-1.The time dependent study indicated that the enlargement of the liver and the liver weight /body weight indexes of the mice 6 hour after oral administration with decoction A at the dosage of 30g（crude drug）.kg-1

or decoction B at the dosage of 12.4 g（crude drug）.kg-1

were obviously increased when compared with that of the normal control mice.The hepatic damage was most serious in 24 hours.The dose dependent study indicated that oral administration with decoction A at the dosage of 16.4

10

3.2

and decoction B at the dosage of 12.4

10.8

10

9.2

8

7.2 g（crude drug） / kg caused increase of liver weight /body weight indexes

and dose dependent damage of the liver tissue.Conclusion:One-time oral administration with large dose of decoction of RRST may induce acute hepatotoxicity and even death in mice in a time and dose dependent manner.