Flame retardant and water repellent finish of polyester fabrics in one bath can shorten the process,save the energy, and give both good flame retardant function and good water repellent function one time. This article realizes successfully flame retardant and water repellent finish of polyester fabrics in one bath by using the products of Dymatic Company. The article explores the prescription and technology of the finishing method and studies application performance of the samples further more.