Objective To explore the effects of schisandrin B (Sch B) on myocardial remodeling and electrocardiogram changes of atrial fibrillation rats. Methods A total of 60 SD rats were randomly divided into normal group, model group, positive control group, low-dose group and high-dose group (12 rats each). Except normal group, rats in other groups were injected with Ach-CaCl₂ mixed solution through tail vein to establish atrial fibrillation model. From the 4th day of modeling, 1 h before Ach-CaCl₂ mixture injection through tail vein injection, rats in positive control group, low-dose and high-dose Sch B group were given intragastric administration of amiodarone 50 mg/kg, Sch 40 mg/kg and Sch 80 mg/kg, respectively, once a day for consecutive 7 days. ECG of each group was recorded during the last caudal vein injection of Ach-CaCl₂ mixture. Echocardiography was used to measure left ventricular ejection fraction (LVEF), left ventricular shortening fraction (LVFS), left ventricular end-diastolic diameter (LVEDD)and left ventricular end-systolic diameter (LVESD). The relative expression levels of collagen Ⅰ (Col Ⅰ) and collagen Ⅲ (Col Ⅲ)mRNA were detected by qRT-PCR, the pathological changes of atrial tissue were observed by HE staining, the myocardial fibrosis was detected by Masson staining, and the relative expression levels of p-Akt, p-mTOR and p-S6K were detected by Western blotting. Results The results of echocardiography showed that LVEF and LVFS were higher, while LVEDD and LVESD were shorter in positive control group, low-dose and high-dose Sch B groups than in model group; Compared with the low-dose Sch B group, the LVEF and LVFS increased significantly, and the LVEDD and LVESD shortened significantly in high-dose Sch B group (P<0.05). The results of qRT-PCR showed that the relative expression levels of Col Ⅰ and Col Ⅲ mRNA were lower in positive control group, low-dose and high-dose Sch B group than in model group; Compared with the low-dose Sch B group, the relative expression levels of Col Ⅰ and Col Ⅲ mRNA were decreased in high-dose Sch B group (P<0.05). The results of HE staining showed that the cardiomyocytes in normal group were in order and dense, and the morphology of the cells was normal with no edema in the interstitium. While those in model group were out of order, intercellular space widened and intercellular interstitium was with edema. The injury of myocardial cells in positive control group, low-dose and high-dose Sch B group was significantly improved. Masson staining showed that the percentage of collagen area in atrial tissue of rats decreased in positive control group, low-dose and high-dose Sch B groups than that in model group; Compared with the low-dose Sch B group, the percentage of collagen area in atrial tissue of rats decreased in high-dose Sch B group (P<0.05). Western blotting results showed that the relative protein expression levels of p-Akt, p-mTOR and p-S6K were lower in positive control group, low-dose and high-dose Sch B groups than those in model group;Compared with the low-dose Sch B group, the relative expression levels of p-Akt, p-mTOR and p-S6K proteins were decreased in high-dose Sch B group (P<0.05). Conclusion Sch B can mitigate rats' atrial fibrillation, improve myocardial injury and cardiac dysfunction, possibly by inhibiting the Akt/mTOR/S6K signaling pathway.