Cardiac Troponins I (cTnI), the Chinese name cardiac troponin I subunit, and cardiac troponin T subunit and cardiac troponin C subunit constitute cardiac troponin complex. Cardiac troponin complex is a calcium regulatory protein, which is used to regulate the contractile function of skeletal muscle and myocardium. When the concentration of intracellular Ca2+ is low, cTnI subunit can inhibit the interaction between troponin and troponin, and then inhibit the formation of myofibrinin. At present, cTnI is only found in cardiomyocytes and is released into the bloodstream after myocardial injury. Therefore, cTnI has high myocardial specificity and sensitivity, and is an important biomarker in the early diagnosis of acute myocardial infarction.