Polymeric microcapsules (MCs) filled with catalyst can be controlled to release the catalyst to initiate the polymerization reaction. In the present work, poly(urea-formaldehyde) (PUF) MCs filled with DBTDL (PUF/DBTDL MCs) were prepared using urea (U) and formaldehyde (F) as the wall shell materials by in situ polymerization. The U-F resins could easily polymerize in the presence of the core material DBTDL to produce PUF polymers, then they deposited on the surface of the DBTDL droplets, forming PUF/DBTDL MCs. The decomposition temperature (T (d)) at 5 % weight loss of PUF/DBTDL MCs was about 245 A degrees C. The application of PUF/DBTDL MCs to cyanate ester resins preliminarily showed the reaction control capability of the MCs due to the slow release of DBTDL through the wall shell.