In order to study whether plasmas exist between powder particles during the densification of low-temperature and fast-forming of micro-forming fields activated sintering technology (Micro-FAST), pure copper powders were chosen purposely in this paper and the micrographs of particle surfaces were examined by high resolution transmission electron microscope (HRTEM). It is found that the oxide layers exist between the surfaces of copper powders before and after the sintering. Moreover, the stacking sequences of atoms at interfacial district (i.e. the joint section of two particles) are obviously different from those within the particles. It is concluded that there is no evidence of existence of plasmas among powder particles during the densification process of Micro-FAST, and the sintering densification mechanism of Micro-FAST is evidently different from that of spark plasma sintering.