Inclusion Criteria:  aged 18-65 years old; a diagnosis of OCD based on The Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5); suffered from severe OCD symptoms over 5 years with substantial functional impairment; the Y-BOCS total score ≥ 25; met the criteria of treatment refractory. Treatment refractory is defined as failed 1) at least three adequate therapeutic trials of serotin reuptake inhibitors (SRIs), with clomipramine being one of the SRIs trials, 2) the use of at least two atypical antipsychotics as augmenting agents, 3) at least 20 sessions of therapist-guided cognitive-behavioral therapy while on a therapeutic dose of an SRIs. These patients have "failed" treatment by demonstrating <25% reduction of Y-BOCS scores or, despite >25% reduction in YBOCS score, by still experiencing significant impairment from their illness.  Exclusion Criteria:  a history of current or past diagnosis of any psychosis according to DSM-5 except for OCD any clinical significant neurological disorder, traumatic brain injury, dementia, or medical illness any contradiction of neurosurgery any current or unstably remitted substance abuse or dependence women who are pregnant or preparing for pregnant severe suicide risk and tendency according to the investigators' judgements participate in any other clinical trials within three months (except for registered studies).