Abstract: Deep eutectic solvents(DESs), low-melting-point binary or multicomponent systems formed by combining hydrogen bond donors and acceptors at specific molar ratios, have garnered increasing attention as promising platforms for drug delivery owing to their superior solubilizing ability, structural tunability, and biocompatibility. This review presents a comprehensive overview of the design principles and physicochemical characteristics of DESs, with a particular focus on their functional roles as solubilizers, permeation enhancers, and stabilizing agents in pharmaceutical formulations. Special emphasis is placed on active pharmaceutical ingredient(API)-based DESs, which incorporate active pharmaceutical ingredients into DESs, with a critical examination of the potential of DES in the engineering of advanced delivery carriers, such as micelles, reversed micelles, nanoemulsions, gels, self-assembled nanoparticles, and immunoadjuvants, and a prospect of the translational prospects, current limitations, and future research directions, aiming to provide some reference for their in-depth research and application in the field of drug preparations.