To explore a method of identifying myocardial capillaries and to use it to observe the effects of ischemic preconditioning on the myocardial capillaries. Anesthetized open chest dogs in ischemic preconditioning (IP) group ( n =6) were subjected to 5min ischemia and 5min reperfusion for 4 cycles before 1 hour of left descending coronary artery (LDA) occlusion followed by 2 hours of reperfusion, while in the ischemia reperfusion (IR) group ( n =6) they were only subjected to 1 hour occlusion followed by 2 hour reperfusion. Myocardial samples in ischemic area were obtained to display capillaries by silver hexamethylenetetramine staining, and their quantitative analysis was conducted by imaging analyzing system. Two growps were then compared. The results showed that myocardial capillaries were clearly shown by silver hexamethylenetetramine, and it revealed that the numerical points density, numerical perimeter density and numerical profile density of myocardial capillaries in ischemic region were obviously increased in IP group compared with IR group. The results suggested the method to identify myocardial capillaries by silver hexamethylenetetramine was reliable and practical, and IP could protect the myocardial capillaries from the damage of ischemia reperfusion.