The film formation process of micro-PS particles (diameter 742 nm) and nano-PS particles (diameter 29 nm) wasstudied by atomic force microscopy and differential scanning calorimetry. During a step heating process, the particles wereannealed for 0.5 h at each selected temperature. It was found that the deformation and interdiffusion temperatures of themicro-PS particles are ca. 120-130℃ and 140-150℃, that of the nano-PS particles are 90℃ and 100-110℃ respectively.The DSC traces of nano-PS particles showed that there was an exothermic peak near T_g after annealing for 0.5 h at theselected temperatures below 90℃; otherwise, the exothermic peak disappeared after annealing at 100℃ or above. Comparedwith the micro-PS pedicles, the sintering process of nano-PS particles occurs at much lower temperature determined by theconfined state of polymer chains with higher conformational energy in nano-particles, and completes in a much narrowertemperature range driven mainly by the larger total surface energy. The film formation process of micro-PS particles (diameter 742 nm) and nano-PS particles (diameter 29 nm) was studied by atomic force microscopy and differential scanning calorimetry. During a heating process, the particles were annealed for 0.5 h at each selected temperature . It was found that the deformation and interdiffusion temperatures of themicro-PS particles are ca. 120-130 ° C and 140-150 ° C, that of the nano-PS particles are 90 ° C and 100-110 ° C respectively. The DSC traces of nano -PS particles showed that there was an exothermic peak near T_g after annealing for 0.5 h at theselected temperatures below 90 ° C; otherwise, the exothermic peak disappeared after annealing at 100 ° C or above. Compared with the micro-PS pedicles, the sintering process of nano -PS particles occurs at much lower temperature determined by theconfined state of polymer chains with higher conformational energy in nano-particles, and completes in a much narrowertemperature range driven mainly by the larger total surface energy.