Abstract: Nano copper decorated multi-walled carbon nanotubes(Cu-MWCNTs)/paraffin composites were synthesized by thermal decomposition of copper(II) formate-carbon nanotubes composite precursor in paraffin using oleylamine as dispersing agent. The phase structure, morphology and phase transition behavior were investigated by means of XRD, TEM and DSC. The thermal sensitivity, thermal expansion, thermal stability and their influencing factors of Cu-MWCNTs/paraffin composites were also studied. The results show that copper nanoparticles of 2-35 nm in size are attached to MWCNTs surface. The phase change temperature and latent heat of Cu-MWCNTs/paraffin composites significantly decrease as compared to that of the paraffin. It is clear that the Cu-MWCNTs/paraffin composites containing 0.2wt% of Cu-MWCNTs are desirable materials for microactuator, with short heating time, small decrease in volume expansibility and excellent thermal stability after being heated for many times.