Most of the commercial flame retardant (FR) polyester fibers are produced using copolymerization with phosphorous FRs. We investigated the fiber properties, dyeing properties, and flame retardancy according to the phosphorous FR type. The physical properties of both the fibers are similar and suitable for textile application. But the dye adsorption rate is much faster in the case of main chain type. This is resulted from higher chain mobility analyzed by glass transition temperature. The main chain type FR polyester fiber adsorbed the dyestuff at lower temperature and reached exhaustion more quickly. And the resistance to chemicals such as acidic and alkaline solutions at high temperature have similar tendency with dye absorption. The migration of dyestuffs and chemicals into the polymer chain has good correlation with chain mobility of the polymers. The main chain type polyester fiber shows better flame retardancy than pendant type polyester, which might be brought about from more rapid degradation into polyphosphoric acid. The main chain type polyester fiber shows better flame retardancy than pendant type polyester. (C) 2008 Wiley Periodicals, Inc.