In this paper, the origin, the evolutionary process of metallogenic magma, the segregation of sulfides and the ore-forming process were studied. Based on geochemical characteristics of different rocks in the Tudun Cu-Ni deposit, the authors infer that the magma belonged to tholeiitic magma series, fractional crystallization occurred in magma chamber and/or during the emplacement process, and there might have occurred assimilation and hybridization during the evolution of the ascending magma. According to the relationship between Cr, PGE and Ni, the fractionation of chromite was likely the main factor leading to sulfide segregation. The diagram of Ti/Y against Zr/Y and the regional geological revolution show that Tudun ore-bearing mafic-ultramafic rocks occurred in an erosion environment after collision.