Phenylpropanoid metabolism is a key secondary metabolic pathway in plants. Through a series of enzymatic cascade reactions using L-phenylalanine as the starting substrate, various metabolites, such as lignin, flavonoids, and phenolic acids, are generated and play a central role in the maintenance of postharvest storage quality, stress responses, and phytohormone signaling in fruits and vegetables. In this review, we systematically summarize the core metabolic processes of this pathway, functional characteristics of key enzymes, their activity-regulation mechanisms, and the synergistic roles of transcription factors and hormone signals in the phenylpropanoid metabolism regulatory network. Furthermore, we review progress in the application of postharvest preservation technologies, including physical, green chemical, and biological regulatory approaches, to modulating phenylpropanoid metabolism. Current research challenges include the incomplete elucidation of crosstalk mechanisms between different metabolic pathways and an unclear understanding of metabolic flux distribution under multi-stress conditions. This review provides a scientific and theoretical reference for basic research and optimization of industrial technology for the postharvest storage and preservation of fruits and vegetables, thereby promoting the development of technologies for maintaining quality, reducing losses, and enhancing efficiency in postharvest production.