Tanshinone IIA (Tan IIA) may exert significant protective effects against heart oxidative stress damage in obstructive sleep apnoea (OSA) syndrome. Chronic intermittent hypoxia (CIH)-triggered left ventricular dysfunction is used in a rat model to mimic CIH in OSA patients. 48 rats were randomly divided into three groups: normal control (NC) group, CIH group and CIH+Tan IIA group with 16 rats in each group. At the end of experiment (day 21), the blood pressure, Plasma ET-1 and NO content, hemodynamic indexes, heart histology, myocardial apoptosis as well as the expression of eNOS, ET-1, ET_A receptor and ET_B receptor were compared among different groups. Tan IIA was able to inhibit the increase of blood pressure induced by CIH. Meanwhile, rat cardiac function in Tan IIA group was evaluated by hemodynamic indexes, histopathological examination. Higher ventricular eNOS activity was induced by Tan IIA with a reduction in both ET-1 and ET_A receptor expression. However, Tan IIA largely inhibited the decrease of ET_B receptor expression. This study demonstrated that Tan IIA has the potential to benefit rat heart against CIH via endothelin system.