This 24-week prospective study (12-week intervention + 12-week follow-up) is a randomized, double-blind, placebo-controlled clinical trial designed to evaluate the therapeutic effects of YishenShujin Decoction, a clinically established herbal prescription, in patients with fibromyalgia (FM). The primary outcome is pain intensity measured by the Brief Pain Inventory (BPI). Secondary outcomes include improvements in the Fibromyalgia symptom scale(FS), revised Fibromyalgia Impact Questionnaire(FIQR), the Short Form-36 Health Status Questionnaire (SF-36), and FM-associated comorbidities. Safety profiles will be systematically monitored. In addition, brain structural and functional MRI will be used in this study to explore the underlying mechanisms.The findings aim to establish evidence for the formula's efficacy and provide insights into its role in FM management.