Objective To investigate the effect of electroacupuncture at Zusanli (ST36) point on the expression of cortical actin-binding protein (cortactin) in smooth muscle cells of rats with irritable bowel syndrome(IBS). Methods Eighty female Sprague-Dawley(SD) rats aged 3 months were randomly divided into 4 groups: normal group, model group, acupoint group and sham-acupoint group, 20 rats in each group. The diarrhea-predominant IBS (IBS-D) rat model was established by high-lactose feeding combined with restraint stress method. Acupoint group was given electroacupuncture at Zusanli point, and sham-acupoint group was given electroacupuncture at external region of 5 mm beside Zusanli point. After treatment, time for the discharge of active carbon through all of the gastrointestinal duct was measured, the contraction of rat proximal colon smooth muscle strips was tested, the expression level of cortactin and the ratio of G/F-actin in the proximal colon were detected by Western blotting method. Results Compared with the normal group, time for the discharge of active carbon through all of the gastrointestinal duct was shortened, and the systolic basic tension of colonic smooth muscle, the expression level of cortactin, and the ratio of G/F-actin in the model group were increased (P<0.05). After electroacupuncture treatment, the time for the discharge of active carbon through all of the gastrointestinal duct in acupoint group was prolonged, and the systolic basic tension of the intestinal smooth muscle, the expression level of cortactin, and ratio of G/F-actin were decreased (P < 0.05 compared with the model group and non-acupoint group). Conclusion Electroacupuncture at Zusanli point can effectively improve the gastrointestinal function of IBS rats and has regulatory effect on the contraction of colonic smooth muscle.