Endometriosis is a condition in which endometrial glands and stroma are found outside the uterine cavity，leading to various symptoms.Professor YOU Zhaoling views endometriosis as a chronic and refractory disease，with its essence being the “blood deviating from meridians” that obstructs the uterine vessels and collaterals.This condition is characterized by a prolonged course，difficult healing，and progressively worsening dysmenorrhea，aligning with the pathophysiological features of “long-standing disease entering the collaterals” and “long-standing pain entering the collaterals” found in the theory of collateral disease.The core pathology is blood stasis obstructing the collaterals.Guided by the theory of collateral disease，Professor YOU Zhaoling proposes a treatment approach for endometriosis that involves addressing cold-heat imbalances，considering the heart，liver，and kidney，resolving phlegm and blood stasis，and treating qi deficiency.Professor YOU advocates for flexible application of therapies that promote qi and blood circulation，warm the meridians，dispel cold，clear heat，remove toxin，resolve phlegm，dissolve masses，and nourish qi and blood.This comprehensive approach helps to smooth the flow of qi，harmonize the organs，and has shown favorable clinical outcomes.