Abstract： Based on modern fascia theory， this study explores the mechanism of penetrating acupuncture of Tiaokou（ST 38）point through Chengshan（BL 57）point in treating scapulohumeral periarthritis，aiming to provide a new perspective for researching the therapeutic mechanism of acupuncture． Physiologically， the mechanical conduction of the anterior superficial line，posterior superficial line，and lateral line in the myofascial meridian system may serve as the theoretical basis for Tiaokou and Chengshan points to treat upper disorders by regulating lower parts of the body． Pathologically， the mechanism of myofascial trigger points（MTrPs）causing local muscle pain and distant referred pain provides partial pathological evidence for the application of penetrating acupuncture of Tiaokou point through Chengshan point．Clinically，taking fascia theory as the core can deepen the clinical application of penetrating acupuncture of Tiaokou point through Chengshan point in treating scapulohumeral periarthritis in terms of diagnosis， treatment，and efficacy evaluation.