Functional dyspepsia is a common clinical disease. Director Deng Guicheng has rich clinical experience in the treatment of functional dyspepsia. This paper summarized the experience of Director Deng Guicheng in the disease diagnosis, especially focused on tongue diagnosis in four diagnostic techniques. Chinese medicine and Western medicine were both referred to avoid the delay of treatment. He thought that the pathogenesis of functional dyspepsia was stomach disharmony, and the method of harmonizing the stomach and directing counterflow qi downward was the basic treatment of functional dyspepsia, including regulating qi and stomach, acrid medicinals opening and bitter medicinals directing things downward, the elimination of the drain, warming the middle and harmonizing the stomach, and eliminating pathological factors. Adjusting mental state should go throughout the whole treatment of diseases.