The Huangshan mafic-ultramafic rock belt in EastTianshanMountains has around much interest among geologists due to the development of many mafic-ultramafic intrusions and nickel-copper magmatic sulfide deposits. A study of the mineral microstructure characteristics and the calculation show that in Sidingheishan intrusion, olivine was the first crystallized mineral, followed by bronzite and diopside, whose crystallization temperatures were about 1100 ℃ and 900~1100 ℃, respectively, and the two minerals in the rock can coexist.