Research design and methods—--a 16-week, double-blind, multiple centers, random parallel controlled study is designed to compare the impact of benfluorex (150-450mg/day, provided by Shandong Xinhua Pharmaceutical Company Limited in China) on glucose control, insulin secretion and its safety with metformin in type 2 diabetic patients. 240 type 2 diabetic patients are to be recruited to receive benfluorex or metformin(1:1). HbA1c, plasma lipid level, insulin and glucose at 0', 30', 120' after a standard meal will be measured before and after treatment, while fasting and postprandial glucose measured 4 times regularly. The change of HbA1c from baseline to the end of treatment will taken as main efficacy criterion, as the changes of fasting and after standard meal glucose and insulin level and plasma lipid level will be taken as secondary criteria. All patient will be given safety monitor at prior and post treatment. Data management and statistical analysis will adopt DAS for Clinical Trial 2.0.