The research on the effects of salt stress on the growth, physiology, and secondary metabolism of medicinal plants was reviewed. In terms of growth, medicinal plants exhibit varying responses to salt stress during germination and growth stages. Low-concentration salt stress may promote seed germination in Salvia miltiorrhiza (if the salt concentration is 20 mmol/L) or enhance seedling growth in Periploca sepium (if the salt concentration is 0.2%-0.5%), while high-concentration stress often inhibits biomass accumulation and induces morphological changes such as alterations in root-to-shoot ratio. At the physiological level, salt stress induces membrane lipid peroxidation in medicinal plants, leading to increased malondialdehyde content and relative electrical conductivity, resulting in cellular membrane damage. To scavenge reactive oxygen species, the activities of antioxidant enzymes such as superoxide dismutase and peroxidase initially increase but subsequently decline. Regarding secondary metabolism, moderate salt stress can enhance the accumulation of pharmacologically active compounds, such as flavonoids, alkaloids, and cardiac glycosides, in various medicinal plants (e.g., Pogostemon cablin, Rumex japonicus, and Taraxacum mongolicum), thereby improving the quality of medicinal materials. In summary, low salt stress may promote the growth of some salt-tolerant medicinal plants, but stress beyond their tolerance range causes cellular damage. Appropriately applied salt stress can stimulate the production of higher levels of active compounds in certain medicinal plants. This review provides insights for selecting suitable soil conditions for medicinal plant cultivation.