Alkaline hydrolysis was carried out on PTMT fibers and the changes in the properties of the hydrolyzed PTMT fiber were investigated. PTMT fibers were hydrolyzed in LiOH, NaOH, and KOH solutions, and the hydrolysis rates of PTMT fibers were in the order of LiOH, NaOH, and KOH. The weight loss increased proportionally with increase in treatment time. In general, the hydrolysis rate of PTMT fiber was lower than PET under the same treatment conditions. Intrinsic viscosity, melting temperature, and density data of the hydrolyzed PTMT fibers indicated that the hydrolysis occurred mainly at the fiber surface. The hydrolysis rate constants of the PTMT fibers were calculated and the hydrolysis activation energy of PTMT fiber obtained from Arrhenius plot was 24 kcal/mol, which was lower than that of PET, 15~19 kcal/mol. Addition of diols such as ethylene glycol and 1,3-propanediol in NaOH solution had little effect on hydrolysis rate, but the presence of n-alcohol increased the hydrolysis rate. The hydrolysis rate was influenced by varying the n-alcohol and its concentrations At 10% (v/v) concentration, the hydrolysis rate increased in the order of methanol, ethanol, n-propanol, and n-butanol. Further increase in the number of carbon did not increase the rate. Thus, the hydrolysis rates of n-hexanol and n-pentanol were even slower than that of n-butanol.