Abstract: Melamine(M)-formaldehyde(F)@n-octadecane(OD) micro-encapsulated phase change composites with OD core and M-F polymer shell were synthesized by nonionic/anionic composite emulsifier via in-situ polymerization. The chemical structure, particle size distribution, micro-morphology and thermal properties of the M-F@OD micro-encapsulated phase change composites were characterized by FTIR, SEM, DSC and laser particle analyzer. The results show that the combination and dosage of different emulsifier produce a significant impact on the morphology and properties of the M-F@OD micro-encapsulated phase change composites. As the anionic/nonionic composite emulsifier is used, the phenomenon of agglomeration of the M-F@OD phase change composites is improved, the particle size distribution of the M-F@OD phase change composites is more uniform, the particle size is further refined which is 0.1-1 μm, providing a high energy storage capacity of 70.86 J/g.