Abstract: Microcapsules containing paraffin were prepared through the in-situ polymerization method using melamine-formaldehyde as wall material. The properties and morphology of the microcapsules were characterized by Fourier-transform infrared spectra (FT-IR), Scanning electronic microscope (SEM), Laser particle size analyzer and Differential scanning calorimeter (DSC). The effects of the molar ratio of formaldehyde to melamine (F/M) on morphology and properties of microencapsulated paraffin were investigated. The results showed that when the ratio of F/M was higher than 4, high degree of cross-linking melamine-formaldehyde resin was obtained and the visible agglomeration of the microcapsules was observed. The phase-transforming point of microcapsules was higher than paraffin, the latent heat of microcapsules decreased as the F/M molar ratio increased.