Target trail emulation is an observational research method, which can use real-world data (such as observational data and historical data) to carry out research design according to the design principles of randomized controlled trials (RCT) when RCT cannot be carried out. The intervention group and the control group were classified by simulating random grouping. Finally a high-reliable conclusion similar to RCT can be obtained. This paper summarizes the basic concepts and application process of target trail emulation based on the effect of statins on the prognosis of myocardial infarction in diabetic patients to provide reference for the application of this method in real world.