Objective To investigate the difference of clinical efficiency and safety in obsessive-compulsive disorders (OCD) treatment with escitalopram or paroxetine.Methods A total of 156 OCD patients were randomly divided into escitalopram group (ESC group) and paroxetine group (PAR group).Yale-Brown Obsessive Compulsive Scale (Y-BOCS),Hamilton Depression Scale (HAMD) and Treatment Emergent Symptom Scale (TESS)were used to evaluate the clinical efficiency and safety before and after1,2,4,6,8 weeks treatment.Results The cure rate(21.79％ vs 17.95％) and effective rate(70.51％ vs 71.79％) had no statistically difference between ESC group and PAR group,and incidence of side effect had no significant difference between two groups(x2 =1.99,P＞0.05).Compared with the group before treatment,HAMD scores were significantly decreased from the first weekend in ESC group,but in PAR group HAMD scores did not decrease until the second weekend,and the differences were also significant(P＜0.05).Conclusion Escitalopram is a safety,effective and well-tolerated drug in the treatment of obsessive-compulsive disorder.