Abstract： This article introduces Professor YANG Yanxian´s clinical experience in treating chronic pelvic inflammation based on the theory of yin fire. Professor YANG Yanxian observed that some patients with pelvic inflammatory disease， despite treatment with antibiotics and bitter-cold Chinese medicine， still exhibited persistent "heat syndromes" that did not subside， leading to chronic pelvic inflammation. These patients often presented with symptoms such as yellowish， foul-smelling vaginal discharge in large amounts， recurrent fever， tenderness in the adnexa， and local infection （increased purulent cells in the vaginal discharge） . Their pulses were often weak and feeble or vacuous and slippery，accompanied by fatigue，a sensation of abdominal heaviness，and general weakness. The underlying pathogenesis is characterized by the deficiency of original qi and the internal generation of yin fire，with damp-heat pouring downward as the manifestation. By applying the theory of yin fire proposed by LI Dongyuan， Professor YANG prescribes a formula， modified Shengyang Penyan Decoction， which can achieve satisfactory therapeutic effects.