Abstract: Melatonin is a type of small molecule indoleamine widely present in both plants and animals, which plays various physiological roles, including regulating seed germination, root development, fruit development, and responding to biotic and abiotic stresses. In recent years, melatonin has also been extensively used in post-harvest preservation of horticultural fruits. This article introduces the synthesis pathways of plant melatonin and the related genes, with a focus on reviewing the physiological functions and mechanisms of melatonin in regulating post-harvest fruit aging, fruit quality, cold tolerance, and antibacterial properties. It analyzes the current issues in the field of plant melatonin research and offers suggestions for future studies, aiming to provide a basis for improving the physiological functions of plant melatonin and the research and development of post-harvest preservation techniques for horticultural fruits.