Objective: To explore the changes of plasma 5-hydroxytryptophan (5-HTP) and tryptophan metabolite levels in children with infantile epileptic spasms syndrome (IESS) before and after adrenocorticotropic hormone (ACTH) treatment, and analyze their correlation with the shortterm efficacy of ACTH. Methods: A total of 35 children with IESS were enrolled. Plasma samples were collected before treatment and on the 14th day of treatment to detect the levels of tryptophan-related metabolites. The children were divided into controlled group and uncontrolled group, and further into controlled group, uncontrolled group and spasm recurrence group for inter-group comparison. Results: The difference in 5-HTP was highly statistically significant between the two groups (p