Twelve-meridian muscle system is a continuous part of meridian system which is a system of qi and blood of twelve-meridian muscle system aggregating, combining, spreading, and aggregating. The flow direction and distribution basically correspond with the direct motion of twelve-meridian muscle system, but there is a difference in the retrograde order with twelve-meridian muscle system. The flow direction is all from the four limbs to the body and finally reaching the head and flowing along the body surface to distribute to the four limbs, body, head, and face. Recently the meaning of meridian muscles is broadly interpreted to the muscle, muscle fascia, tendon, ligament, cartilage, and articular capsule and this can cover the modern pain treatment and theories. The area is diverse from MPS to the massage and chiropractic. With this study as a momentum, we expect the meridian systemic and physiological theories of oriental medicine in the pain treatment to be more appreciated for their merits with more active studies about meridian muscles.