Abstract: With using poly-(melamine-formaldehyde)(PMF) as the shell and Trimethylolpropane tris (3-mercaptopropionate)(TMPMP) as the core,TMPMP@PMF for epoxy based hardner was synthesized by in situ polymerization process.The influences of the content and type of emulsifier,the mass ratio between the core and the shell,reaction time and temperature,pH value on the properties and structural of obtained micro-encapsultes were studied.The results show that an optimal synthesis condition can be obtained with the content of 2wt% TMPMP and the mixing mass ratio of 2:1 between TMPMP to PMF.The obtained TMPMP@PMF encapsulates have stable morphology,closed shell structure and heat resistant performance.In addition the pressure-sensitive hardner of TMPMP@PMF/EP was prepared by mixing TMPMP@PMF and epoxy based hardener (EP).The results show that the microcapsules can be timely fractured under the action of external force,so EP also can be solidified in a short time at room temperature or even lower temperature (about 0℃),and the curing performance and the impact resistant performance of TMPMP@PMF/EP hardner can be effectively improved.