Objective To evaluate Janus kinase (JAKs) and Suppressors of cytokine signaling(SOCSs) expression in myocardium after endurance training. Methods 30 male Sprague-Dawley rats undertook 10 weeks grade treadmill training program and were sacrificed at 0 and 24 h respectively after the last exercise. JAK1,JAK2,JAK3 and SOCS1 ,SOCS2,SOCS6 expression in the myocardium were determined by im munohistochemistry method. Results The percentage of JAK1 positive cell significantly increased immediately after last running and recovered to the sedentary level 24 hrs after exercise;The percentage of JAK2 positive cell significantly increased immediately after last running and continuously at a higher level 24 hrs after exercise (P<0.01;P<0.05); JAK.3 showed no significant change either immediately or 24 hrs after exercise (P>0.05). The percentage of SOCS1 and SOCS2 positive cell also significantly increased both immediately and 24 hrs after exercise (P<0.01 ;P<0.05). However, the percentage of SOCS6 positive cell showed no significant change either immediately or 24 hrs after exercise(P>0.05). Conclusion Endurance training could induce different responses of JAK1,JAK2 and JAK3. The increased expressions of JAK1 and JAK2 might indicate the changes of JAK/STAT signal pathway in regulating myocardial function. The increased expressions of SOCS1 and SOCS2 after endurance training might indicate the increased exertion in regulating JAK/STAT signal pathway in cardiac muscle.