Aim To explore the objective evidence of ischemic preconditioning (IP) in patients with stable angina (SA).Methods sixteen patients with SA underwent two times of treadmill exercise tests(TET) at the interval of 10 minutes according to Bruce protocal. The appeared rate and time of chest pain, maximal value and duration of ST segment depression, arrhythmias occurred during TET were analysed for different two tests. Results 9 patients (56.3%) complained of chest pain in the first test, however, only 4 of them (25%) did in the second one (P<0.01). The occurred time of chest pain was 2.24±0.2 min in the first test, 3.8±0.4 min in the second one (P<0.05). The maximal value of ST segment depression decreased from 0.18±0.07 mV in the first test to 0.12±0.04 mV in the second one (P<0.01), and duration of ST segment depression was down from 6.42±0.8 min in the first test to 4.1±0.5 min in the second one (P<0.01). The rate of arrhythmia decreased from 43.8% in the first test to 18.8% in the second one (P<0.01). Conclusions The present data demonstrated that transient ischemia of myocardium could result in ischemic preconditioning phenomenon, and protected heart from more serious damage at the definite interval of time.