Reactive　kinetics　of　the　toluene-2,　4-diisocyanate　(TDI)/polyhexa-methylene　adipate　diol　(PHA)　bulk　polymerization　with　or　without　catalyst　was　studied　by　means　of　titration　analysis.　The　results　indicate　that　the　polymerization　of　TDI/PHA　is　a　second　order　reaction,　and　the　activation　energy　is　41.58　kJ/mol　without　catalyst　and　reduced　to　34.02　kJ/mol　with　dibutyltion　dilaurate　(DBTDL)　as　catalyst,　indicating　that　the　catalyst　can　decrease　the　activation　energy　and　improve　the　reaction　rate.　The　reaction　system　viscosity　increases　at　the　later　reaction　stage　whether　the　catalyst　in　the　system　or　not,　and　the　reaction　is　turned　gradually　to　the　diffusion　control　and　deviates　from　the　second　order　reaction　kinetics.