Alginates are polysaccharides found in brown seaweeds, and the most abundant marine biopolymer and, after cellulose, the most abundant biopolymer in the world. Alginate purification process from brown algae is simple. This goal is feasible by using of diluted mineral acid and sodium carbonate on dried brown algae. The conventional use of alginate as an excipient in drug products generally depends on its gel-forming and stabilizing properties. Alginate gel can be prepared during gelation process with three methods of syringe or droplet, extrusion and fluid methods. The main benefits of alginates, such as biocompatibility and biodegradability, have led to an increase in scientists' desire to use alginate as a platform to promote the new delivery systems of nanodrugs in recent decades. Release of water-soluble drugs from the alginate gel matrix is generally via diffusion, while low-solubility drugs are released through the alginate matrix erosion. The potential use of the various qualities as pharmaceutical excipients has not been evaluated fully, but alginate is likely to make an important contribution in the development of polymeric delivery systems. The purpose of this narrative review is to explain the structure, properties, method of preparation and application of alginate nanoparticles in pharmaceutical systems.