Pretreatment process for electroless nickel coating on ultrafine glass microspheres with an average diameter smaller than 10μm was studied. Through comparative experiments, three-step pretreatment process including washing, coupling and activating was selected to pretreat ultrafine glass microspheres with supersonic. Then the amount and distribution of palladium activate sites absorbed on the surface of microspheres were measured by energy-dispersive X-ray spectroscopy (EDX). It was found that the content of palladium was increased obviously because of addition of coupling treatment and optimization of pretreatment parameters such as agitation method and loading weight, meanwhile palladium was distributed more uniformly due to the action of supersonic. In addition, pretreated microspheres were placed in an alkaline plating solution with supersonic and nickel coated microspheres were obtained. Then morphology and composition of the coating were characterized by scanning electron microscopy (SEM) and EDX. The results proved that EDX results of palladium could characterize the result of pretreatment effectively. The low density Ni coated microspheres may be utilized for manufacturing conducting materials for EMI shielding applications.