Provided is a composition for a heat-shrinkable tube, comprising: a base resin; and a flame retardant, wherein the base resin comprises chlorinated polyolefin resin and polyolefin elastomer, wherein the chlorinated polyolefin resin comprises chlorine in an amount of 30 to 40% by weight based on the total weight thereof, and the polyolefin elastomer has a melting point of 95 to 120° C., and an amount of the chlorinated polyolefin resin is 40 to 60 parts by weight and an amount of the polyolefin elastomer is 20 to 40 parts by weight, based on 100 parts by weight of the base resin.