By means of dolomite geochemical methods, an elaborate study was carried out on dolomitized rocks which are of widely distributed permian Fengcheng Formation at Wuerhe-Fengcheng area in the northwest margin of the Junggar Basin. Based on the geochemical element analysis combined with the temperature and paleosalinity analysis, it was concluded that the Fengcheng Formation dolomite formed on a higher salinity and low temperature environmental volcano hydrothermal activities also have had a certain influence on the dolomite formation; dolomitic rock formation occurred mostly in the low diagenetic stage; little occurred in the late diagenesis burial period and overall dolomitic rocks formed in the early diagenetic stage of continental saline lakes.