Abstract: To overcome the latent problems of microcapsules in their applications, two kinds of PCM (phase change materials) nanocapsules with different melting point are synthesized. The particle size as well as the heat storage capacity is investigated by TEM and DSC. Cotton knit fabrics are then treated with above two kinds of PCM microcapsules by a pad-dry-cure method with binder. The properties of thermoregulation and air permeability of the finished fabrics are evaluated by infrared thermometer and fabric air permeability meter. It is found that the diameters of the microcapsules are around 150 nm. The ratio by volume of shell to core is 1:1. The melting peak points are 37.1℃ and 33.1℃ respectively. The phase change enthalpies are 56.2J/g and 57.8J/g. After treatment, the fabrics are capable of absorbing about 7000 J/m2 heat. The temperature changing rate of the treated fabric slows down as the PCM experiences phase change, which demonstrates excellent thermoregulation function. The air permeability slightly reduced with respect to the add-on binder and microcapsules.