Antibiotics are used as a first-choice to inhibit microbial growth since the discovery in the first half of the 19th century. Nevertheless, the widespread use of antibiotics has resulted in the emergence of antibiotic-resistant strains that is one of our century problems. Concerns about antibiotic resistant is so serious which huge budget is allocated for discovery of alternative drugs in many countries. Bacteriocin is one of these compounds which was first discovered in 1925, released into the medium by E. coli. Bacteriocins are antimicrobial peptides or proteins ribosomally synthesized by many bacterial species. The use of this antimicrobial molecules in food industry obviate consumers need to safe food with least interference of chemical substances. Nisin, the most well-known bacteriocin, is the first bacteriocin found its way to food industry. Despite the widespread application of bacteriocins, resistance is seen in some species. Although it’s exact mechanism is not clear. So according to the today’s world need to find effective methods to control pathogens, studies of bacteriocins as a substitute for antibiotics are so important. The present review has studied the structure and activity of five classes of bacteriocins from gene to function in gram positive bacteria. Keywords: Bacteriocin, Antimicrobial activity, Structure, Classification