OBJECTIVE： To establish the method for the determination of plasma concentration of magnesium isoglycyrrhizinate in portal vein and peripheral venous blood of patients underwent liver resection， to further validate and evaluate pharmacokinetic characteristics， rational and safe use of drugs in the clinic. METHODS： 31 patients underwent liver resection in our hospital during Oct. 2014-Mar. 2015 were given magnesium isoglycyrrhizinate intravenously at the beginning of surgery. Portal vein and peripheral venous blood of patients were drawn at 1 hour after drug use， and HPLC-UV detection method was used to determine the plasma concentration of drug. RESULTS： The retention time of isoglycyrrhizinate magnesium was 4.5 min， which showed a good peak shape， and was not interfered with the determination by plasma endogenous peak. The plasma concentration ranged from 0.55 to 55.00 mg/L. The minimum quantitative concentration was 0.55 mg/L. The extraction recoveries were 84.7％-87.1％， and method recoveries were 101.2％-105.4％， and RSDs of intra-day and inter-day were less than 6 ％. Plasma concentration of magnesium isoglycyrrhizinate in portal vein blood was significantly higher than in peripheral vein blood of patients underwent liver resection （close to 2 times）； and plasma concentration was not affected by primary liver diseases and underlying diseases such as cirrhosis. CONCLUSIONS： The method is simple and has high recovery rate of extraction， high accuracy and high sensitivity. It can meet the needs of pharmacokinetic study. After the application of magnesium isoglycyrrhizinate during liver resection， there is higher blood concentration of magnesium isoglycyrrhizinate in portal vein， which is beneficial to protect liver cells and improve liver function. It is suitable during perioperative period of liver.