The Pobei mafic-ultramafic belt is an impotant Ni-Cu sulfide metallogenic prospective province in Beishan area, eastern Xinjiang. About 20 intrusions (e.g., Bijiashan, Hongshishan, Cihai, Poyi, Poshi and Luodong) were recognized along the fault in this area and almost all the intrusions are associated with Ni-Cu sulfide deposits. The Hongshishan mafic-ultramafic complexs are located in the eastern part of the Pobei mafic-ultramafic belt and the southern part of the Baidiwa-Yunihe fault in this area. They intruded into quartz schist of the Lower Carboniferous Hongliuhe Formation. They are mainly composed of dunite, peridotite, troctolite, pyrox-enite, olivine gabbro, gabbro and diorite. These rocks were emplaced in two stages. The first stage consists of peridotite and olivine gabbro, and the second stage comprises gabbro and diorite. The dunite, pyroxene peridotite and troctolite are the host rocks for Ni-Cu sulfide ores. The platinum-group elements and Re-Os isotopic compositions of ore and rocks from the Hongshishan Ni-Cu sulfide-bearing mafic-ultramafic intrusions were analyzed, and the result shows that the total PGE content is quite low, ranging from 0.54×10^-9 to 15.84×10^-9 and increasing with the increase of sulfide content. The PGE primitive mantle-normalized patterns display a positive slope and low fractionation between IPGE and PPGE. PGE, Cu and Ni are depleted relative to the primitive mantle with low and a narrow Pd/Ir range (3.19～10.5), indicating a weak influence of later hydrothermal alteration. Furthermore, the Ir displays positive correlations with Pt, Pd, Os, Ru and Rh, indicating a weak contribution of the fractionation and the partial melt to PGE depletion. The Cu/Pd ratios(73×10³～1 670×10³)and Ti/Pd ratios (87×10³～2 857×10³)of these rocks suggest that sulfur in the primary magmas had reached saturation, and immiscible sulfides droplets were segregated from silicate magmas before their emplacement. The relationship between Ni/Cu and Pd/Ir indicates that the parental magma was high-magnesium basaltic magmas. Their γ_Os(t) and (¹⁸⁷Os/¹⁸⁸Os)_i are variable,ranging from +18 to +282 and from 0.148 3 to 0.481 3, respectively, suggesting that abundant crustal material was mixed with the ascending magma. The fractionation of olivine and contamination by crustal material probably triggered the sulfide saturation and segregation and the Ni-Cu-(PGE) mineralization as well. The intrusions were generated from the magma that had undergone crystallization differentiation of olivine and segregation of sulfides.