Background: Infections such as common colds, influenza, acute upper respiratory infections, bacterial gastroenteritis, and urinary tract infections are usually diagnosed according to patients' signs and symptoms. This study aims to develop a scale for the diagnosis of infectious diseases based on the six excesses (Liu Yin) etiological theory of Chinese medicine (CM) by the Delphi method. Methods: A total of 200 CM-guided diagnostic items measuring signs and symptoms for infectious diseases were compiled from CM literature archives from the Han to Ming dynasties, CM textbooks in both China and Taiwan, and journal articles from the China Knowledge Resource Integrated Database. The items were based on infections and the six excesses (Liu Yin) etiological theory, i.e., Feng Xie (wind excess), Han Xie (coldness excess), Shu Xie (summer heat excess), Shi Xie (dampness excess), Zao Xie (dryness excess), and Huo Xie (fire excess). The items were further classified into the six excess syndromes and reviewed via a Delphi process to reach consensus among CM experts. Results: In total, 178 items with a mean or median rating of 7 or above on a scale of 1-9 from a panel of 32 experts were retained. The numbers of diagnostic items in the categories of Feng (wind), Han (coldness), Shu (summer heat), Shi (dampness), Zao (dryness), and Huo (fire) syndromes were 15, 22, 25, 37, 17, and 62, respectively. Conclusions: A CM-based six excesses (Liu Yin) evaluation and diagnosis (SEED) scale was developed for the evaluation and diagnosis of infectious diseases based only on signs and symptoms.