Abstract: Objective: To determine the effect and side effect of ritodrine in the premature labor and investigate the clinical significance.Methods: One hundred cases of premature labor were randomly divided into observation group and control group.Observation group consisted of 60 cases were given with ritodrine at 0.05 mg/min concentration firstly,and the concentration was added gradually until the uterine contraction was vanished and the medication was continued for 12-18 hours,then the medicine taken orally last for 7 days.Control group consisted of 40 cases were given with magnesium sulfate intravenously,the first 4 g was given within 30 minutes,then 1-2 g per hour was given until the uterine contraction was vanished.The success rate of fetus protection,the time of uterine contraction vanished,the incidence of hypopotassaemia,the changes of heart rate,the effect of prolong gestational age,the rate of postpartum hemorrhage rate,neonatal weight and the Apgar score were compared between the two groups.Results: Percent of failure cases is 11.7% in observation group and 12.5% in control group;prolong gestational age is(1.00±0.7) week in observation group and(0.87±0.6) week in control group,which was shown no significant difference between two groups(P>0.05).The time of uterine contraction vanished in observation group was shorter than in control group(P<0.05).The incidence of hypopotassaemia was higher in observation group(P<0.01).The rate of postpartum hemorrhage,neonatal weight and the Apgar score were no significant difference.Conclusions: Ritodrine can inhibit uterine contraction of pregnant woman which prevent the occurance of premature labor effectively,but the incidence of hypopotassaemia and other side effects will be cautioned.