Abstract： This paper introduces the clinical experience of Professor SHEN Yuanliang， a physician of the Shaoxing School， in differentiating and treating ankylosing spondylitis （AS） based on the theory of latent pathogen. Professor SHEN posits that latent pathogens are of two types： exogenous latent pathogens and endogenous latent pathogens. He identifies the core pathogenesis of AS as kidney qi deficiency，with the latent pathogen being triggered by a new exogenous contraction. The therapeutic strategy should adhere closely to the pathogenesis， employing the principle of tonifying the kidney and expelling the latent pathogen. In clinical practice， he frequently uses his experienced prescription，the Wenshen Juanbi Decoction，with modifications，and is skilled in the application of drug pairs and drug combinations for formula modification. He also emphasizes the concurrent management of comorbid conditions such as uveitis，iritis，and inflammatory bowel disease，often achieving satisfactory therapeutic outcomes.