Abstract: The characterization of process mineralogy of the Haicheng magnesite ore has been investigated through optical microscope,XRD and chemical analysis.The results show that besides the valuable mineral magnesite the primary gangue minerals were talc,dolomite,quartz,clinochlore,apatite,little pyrite and limonite in the ore.The dissemination size of the ore is maldistribution.The dissemination size of magnesite minerals were thick and interspersed with other gangue minerals,and easily to be dissociated.