Objective:To investigate the protective effect of Intravenous Injection of Radix Astragali seu Hedysari on acute myocardiac infarction (AMI) in anesthetized dogs. Methods: Twenty health dogs were treated by ligating descending anterior of coronary with two-step method. The changes of electrocardiogram before and after ligation were recorded. After 4 hours myocardium were taken out and dyed with NBT to make sure of the extent of myocardiac infarction.Results: Intravenous Injection of Radix Astragali seu Hedysari could decrease the lethality of AMI, ameliorated ST changes on electrocardiogram induced by AMI, and reduced infarction area. Conclusions: Intravenous Injection of Radix Astragali seu Hedysari is effective in the treatment of AMI in anesthetized dogs.