Lumbar anesthesia is the preferred anesthetic approach for puerperae undergoing cesarean section in China. To observe the safety of administering different doses of ropivacaine for cesarean section and its pharmacodynamic mechanism, we randomly divided 180 pregnant women undergoing cesarean section into three groups: group A, 10 mg ropivacaine (0.50%); group B, 12 mg ropivacaine (0.50%); and group C, 14 mg ropivacaine (0.50%). Pharmacodynamic index, anesthesia quality and incidence of untoward reactions of each group were observed. Group A performed the poorest and group C the best in evaluation of sensory and motory block (P less than 0.05). With regard to evaluation of hemodynamic index, hemodynamic parameters of the three groups had significant differences after medication; mean arterial pressure (MAP) of patients in group B decreased at time points T1, T2 and T3 and heart rate (HR) became much higher at T1 (P less than 0.05); MAP of the patients in group C decreased at T1, T2, T3 and T4, but HR became higher at T1 and T2 (P less than 0.05); HR of group B was higher than that of group A at T1 (P less than 0.05); MAP of the patients in group C had a significant decrease at T1, T2, T3 and T4, but HR became higher at T2 (P less than 0.05); MAP of patients in group C significantly decreased compared to group B at T1 and T2, but HR became higher at T2 (P less than 0.05). Fluctuation of oxyhemoglobin saturation (SpO2) of all patients was between 95% and 99%. There was no occurrence of myocardial ischemia or arrhythmia. 1-min Apgar score of neonates of the three groups had no significant difference (P0.05). The incidence of adverse reactions of the patients in group C was much higher than that of the patients in the other groups (P less than 0.05). Twelve mg ropivacaine (5%) is the most suitable dose for pregnant women undergoing cesarean section as it can achieve a sound anesthetic effect and high safety and, moreover, has little influence on respiratory and circulatory functions.