Aim To improve the method of making myocardial infarction models in dogs and to form transmural myocardial infarction. Methods 16 healthy adult mongrel dogs were randomly divided into control group （n＝8） and experimental group （n＝8）. The myocardial infarction was established. In control group, the left anterior descending coronary artery was ligated. While in experimental group, the left anterior descending coronary artery and first diagonal branch were ligated. After 6 weeks, cardiac general morphology and histopathology were observed. Results After 6 weeks, there were 6 dogs survived in control group and 5 dogs survived in experimental group, and the survival rates were 75.0% and 62.5% respectively. There was no statistically significant difference at survival rate in two groups （P＝0.590）. Of the survived 6 dogs in the control group, there were 2 dogs that myocardial infarction could be seen clearly by cardiac general morphology and histopathology Of the other 4 dogs, there was no myocardial infarction by cardiac general morphology, but micro-infarction was observed by histopathology. Of the survived 5 dogs in the experimental group, myocardial infarction could be observed clearly by cardiac general morphology and histopathology in all dogs. There was significant difference in the dog number of transmural myocardial infarction in two groups （P＝0.022）. Conclusion The ligation of the left anterior descending coronary artery and first diagonal branch in dog can form transmural myocardial infarction, which is an effective and reliable method for preparation of myocardial infarction model.