Based on the theory of "small intrusions forming large copper-nickel sulfide deposits" and the principle of rock magnetism,the authors chose the magnetic parameter Q value(the ratio of remanence intensity and magnetic intensity)closely related to the cooling rate of magma to study the thermodynamic ore-forming process of the Xiarihamu Cu-Ni sulfide deposit in East Kunlun,Qinghai Province.Statistics of 3682Q data from 90 drill holes in the Xiarihamu Cu-Ni sulfide deposit show that there exists no significant difference of Q values between intrusive rocks and metamorphic rocks,and there is no obvious high Q value zoning over the magma contact zone;the authors thus consider that hot baking was not serious in the magma contact zone due to the insignificant temperature difference between the metamorphic rocks and the magmatic rocks, which both lay in the deep underground.The spatial distribution of the Q values shows that the tectonic weak zone represented by the high Q anomaly belt has two positions:one is located in the lower part of the contact zone of the rock mass,and the other lies along the contact zone between the interior and the upper part of the rock mass.According to the Q values,it is inferred that fluid first penetrated from the lower contact zone,and then migrated into the contact zone between the interior and the upper part of the rock body.The fluid that penetrated into the weak tectonic belt might have played two kinds of roles:one was to dissolve sulfide minerals in the weak tectonic belt and thus had the ore-breaking effect,and the other was to perform infiltration and caused the migration of the ore-forming elements,thus exerting the ore-forming effect.However,the examples of applying magnetic parameter Q value to the study of the thermodynamic process are relatively less,and this paper is only an attempt to deal with this problem.