The macrokinetics of poly(trimethylene terephthalate) (PTT) polycondensation reaction during the high-vacuum process was studied. The results showed that PTT polycondensation reaction may be considered as a second-order reaction and thermal degradation is negligible in mathematical handling. The intrinsic viscosity versus time undergoes two different processes according to temperature. The apparent reaction rate constants and apparent activation energy of PTT polycondensation reaction are smaller than those of PET. Under efficient stirring, PTT polycondensation reaction is still reaction-controlled and the role of devolatilization could be neglected even during the high-vacuum process. (C) 2004 Wiley Periodicals, Inc.