In order to establish the standard manufacturing condition of PET flame retardant sheets, physicochetnical properties of the samples made by the conventional flame-retardant finishing were systematically investigated, including compatibility among flame retardant agent and finishing auxiliaries, surface property, and wicking property. From this results, the addition of washing and renapping process after the shearing process was required for the more effective in producing PET flame-retardant sheet by the standard finishing. The effect of the modification of the regular flame retardant finishing process was studied by FTIR, TGA, and flame retardancy test.