Chronic low back pain (CLBP) is the most prevalent form of chronic pain, and the most common reason for disability in working-age population [2]. CLBP has also been reported associated with many abnormal brain anatomy and function which includes the reduction in cortical gray matter in the bilateral dorsolateral prefrontal cortex (DLPFC), thalamus, brain stem, primary somatosensory cortex, and posterior parietal cortex. [3-5] There are already many studies that demonstrated abnormal cortical function for people with CLBP [6-10]. Meanwhile, DLPFC was also reported to be influenced by many pain process which included pain modulation [11-13], placebo analgesia [14, 15], pain control [16, 17]or pain catastrophizing[18]. And recent report has showed that effective treatment of chronic back pain patients reverses abnormal DLPFC function[19]. Meanwhile, epidural steroid injection has been performed in clinical for routinely managed for low back pain patients. Patients refused or have no indication for surgery or have little response to rehabilitation may consider this management. There was good evidence for short- and long-term relief of chronic pain secondary to disc herniation with local anesthetic and steroids[20, 21]. However, the impact of this treatment on functionalMRI (fMRI) has never been investigated. The investigators research will try to solve this issue.