As a complex microecosystem, the gut microbiota has a close relationship with the host and plays a central role in regulating physiological functions related to nutrition, immune system activation and host defense. Tryptophan (TRP), an essential amino acid, must be obtained from the diet. TRP participates in a variety of physiological functions and affects the growth and health of the human body. Abnormal TRP metabolism has been associated with many diseases. One of the main ways in which the gut microbiota interacts with the host is through metabolites. Tryptophan catabolites produced by gut microbiota are important signaling molecules in the microbial community and in host-microbe crosstalk, and play an important role in physiological and pathological processes. This study describes research progress on the classification and function of gut microbiota, the influence of gut microbiota on TRP metabolic pathways and related diseases, and the potential mechanism of these effects, and discusses new clinical research for disease pathogenesis and treatments.