Guided by the TCM theory of “the lung and large intestine are interrelated”, this paper analyzes severe pneumonia with Qi-Yin deficiency syndrome. Combined with the connotation of Zang-Fu viscera correlation theory and modern research on lung-intestine correlation, it sorts out the core pathogenesis of simultaneous lung and intestinal disease complicated with deficiency of both Qi and unobstructed Fu Qi in this disease, and elaborates the formula logic and clinical application value of Xinhuanglong Decoction for replenishing Qi and nourishing Yin, unblocking Fu organs and clearing heat. Most patients with severe pneumonia are accompanied by varying degrees of gastrointestinal injury and severe systemic inflammatory response. The elderly and patients with chronic illnesses and physical weakness are more prone to develop a complicated pathogenesis of intermingled deficiency and excess. With simultaneous purgation and tonification, Xinhuanglong Decoction can effectively improve gastrointestinal motility and reduce the level of inflammatory indicators, shorten the duration of mechanical ventilation and ICU hospitalization, and is more suitable for elderly and chronically ill patients with severe pneumonia of Qi-Yin deficiency syndrome. This prescription embodies the TCM diagnosis and treatment idea of simultaneous treatment of lung and intestine, possesses high clinical application potential, and can provide references for integrated traditional Chinese and Western medicine treatment of severe pneumonia, worthy of further verification and promotion through large-sample clinical studies.