Urea formaldehyde/Epoxy(UF/E) self healing microcapsules were prepared by in situ polymerization using ammonium chloride as UF/E self healing microcapsule modifier. To find out the effects of the content(by mass, the same below) of ammonium chloride on the particle characteristics and encapsulated indicators of UF/E self healing microcapsules, chemical structure and thermal stability were characterized by FTIR, TGA and ESEM. The results show that the yield and core content of UF/E self healing microcapsules reduce after increase of ammonium chloride/UF prepolymer mass ratio. When the mass ratio of ammonium chloride/UF prepolymer is 1150%, both the yield and core content reach the highest levels which are 7905% and 6840%, respectively. UF/E self healing microcapsules are spherical and full, with rough surface and good overall dispersion, which are conducive to the combination of cement based materials. With the increase of ammonium chloride content, the pH value of the reaction system decreases, the accumulation of urea formaldehyde resin particles on the surface of microcapsules is accelerated, and the particle size of microcapsules is increased. By analyzing the chemical structure and thermal stability of UF/E self healing microcapsules, it is proved that urea formaldehyde resin shell material encapsulates epoxy resin core material successfully and has good thermal stability.