Methods: This is a randomized wait-listed controlled clinical trial. Eligible patients with history of at least 3 months of PNSLBP will be randomized in to two groups, 45 patients each. The first group will be given wet-cupping treatment at two acupuncture points of urinary Bladder (BL) meridians among the BL23, BL24 and BL25, 6 times within 2 weeks. The second group will serve as a control group. Usual care, including providing brochures for exercise, general advice for PNSLBP and acetaminophen, will be allowed in both groups. Separate assessors participated in the outcome assessment. Investigators will use the 0 to100 numerical rating scale (NRS) for pain, the McGill Pain questionnaire for pain intensity (PPI) and the Oswestry Disability Questionnaire (ODQ), and to assess acetaminophen use and safety issues.