Abstract: Through the in-si t u polymerization method , a kind of phase change materials microcapsule was preparedby using melamine-urea-formaldehyde resin as the shell material and a phase change material as the core , of whichthe melt point and phase change enthalpy are 24 ℃and 225. 5 J / grespectively. The penet rability and st rength of microcapsule were investigated by altering the mole ratio of urea to melamine. The thermal damage mechanism is thatthe phase change materials leak out f rom the microcapsule when they are heated , and the breakage of the shell wasdue to the thermal expansion of the core and shell materials at high temperature. The damage temperature of the microcapsule shell can be obtained by TGA. The st rength of the shell was evaluated through observing the surfacechange under pressure by mean of scanning elect ron microscopy. The penet rability of the microcapsule was characterized in ethyl alcohol by mean of 752 spect rophotometer. As a result , the average diameter of the microcapsule issmaller than 5μm , and the particle size is cent ralized when the dropping rate of the solidifying solvent is less than018 mL/ min. The mass loss temperature of the microcap sule can be further enhanced up to 30 ℃while the reactionsystem contains 20 % (mass f raction) urea. The microcapsules do not rupture under a pressure of 6. 0 MPa , and thecore material leaks out very slowly from the microcapsule in ethyl alcohol.