2. Randomized controlled single-blind study: The OCD patients are randomly assigned into pharmacological treatment, psychological treatment or pharmacological combined with psychological treatment. Psychological treatment: every six or so patients can establish a closed structured group. Each group will be treated for 12 sessions, for once a week, 120 minutes at a time. The 1-3 session will be psychological education on the topic of OCD and cognitive behavioral therapy; The 4-6 and 8-10 session will do step by step exposure and response prevention(ERP) training; the 7th an 11th session will invite family members or other caregivers of OCD patients for a education about OCD cognitive behavioral therapy to facilitate patients to complete ERP homework and give them some social supports; the final session will be self treatment evaluation and long-term treatment guidance. Pharmacological treatment: This study choose the SSRIs(Selective Serotonin Reuptake Inhibitor:sertraline, fluvoxamine, initial dose of 50 mg, the dose can be adjusted once a week, and the maximum dose should under the instruments ) approved by SFDA(China Food and Drug Administration) for OCD treatment which will last 12 weeks. Patients with sleep disorder can combined with Benzodiazepines less than two consecutive weeks; combination with other psychotropic drugs are forbidden. Pharmacological combined with psychological treatment: every six or so patients can establish a closed structured group which is same as the psychological treatment group; patients start to take medicine at the same time, use of the medicine is same as the pharmacological treatment group.