Abstract: The article studied the effect of alkali treatment conditions on the weight reduction,structure and morphology of PTT fibers,and the optimal process conditions were determined by orthogonal design analysis.The results showed that many pits are distributed on the surface of the fibers.The mechanical property has decreased a little,but the wettability and dyeability have improved.When the weight less is 15.97%,their dyeability obviously increases.When the concentration of promoter(1631) is 0.003 mol/L,the optimal process conditions for alkaline treatment of PTT fibers are as follows: the concentration of sodium hydroxide solution,0.875 mol/L;treating at 90℃for 60 minutes.