Durable press finishing of cotton fabrics with polycarboxylic acid increases fabric wrinkle-resistance at the expense of its mechanical strength.Severe tensile strength loss is the major disadvantage for wrinkle resistant cotton fabrics.Tensile strength loss of cotton fabric crosslinked by a polycarboxylic acid can be attributed to depolymerization and crosslink of cellulose molecules.Measurement of the molecular weight of cotton fabric before and after crosslinked by polycarboxylic acids can offer a possibility of direct understanding of the depolymerization.In this research,a multiple angle laser light scattering photometer was used to determine the absolute molecular weight of cotton fabric treated with BTCA at different pH and then hydrolyzed with 0.5 M NaOH solution at 50℃ for 144 h.The results indicate that average molecular weights of cotton fabric treated with polycarboxylic acids at different pH are almost the same.