Abstract: Objective To evaluate Janus kinase(JAK)s and SOCS1 expression in myocardium induced by acute exercise in order to understand the possible regulating mechanism of SOCS1 in JAK/STAT signaling pathway in exercised heart. Methods Male Sprague-Dawley rats were submitted to continuous graded treadmill running, then were sacrificed at 0, 1, 3, 5, 12 and 24 h respectively after the exercise. JAK1, JAK3 and SOCS1 expressions in the myocardium were determined with immunohistochemistry. Results JAK1 expression significantly increased immediately after running in comparison with control group, peaked at 1~5 h, and remained high at 24 hr after exercise; in contrast, JAK3 and SOCS1 expressions significant decreased from 1h to 5h after running, then gradually back to sedentary level 12h after exercise; Conclusion Acute exercise induced the different responses of JAK1 and JAK3, which indicated the different function of JAKs in exercised heart, SOCS1 may involve in regulating JAK/STAT3 signal pathway in the exercised heart.