The investigated district is located in the middle of the Micang Mountains at the juncture of southern Shanxi and northwestern Sichuan. The bottom Stratum in this district is proterozoic metamorphic rocks (Hadiya Group). From top to bottom,there are Tiechuanshan Formation, Mawozi Forma- tion and Houhe Formation, intruded and separated by basic and acidic magmas of the Jinning stage. They are distributed discontinuously. Assimilation, cotami- nation and metasomatism are clear along the contact zone of basic bodies with siliceous dolomite and in places where basic bodies contain more xenolithes of siliceous dolomite. The amphibolites are distributed along the contact zone and found in the intrusive bodies with large quantities of siliceous dolomite xeno- lith, and the tatter is larger in scale than the former. Among the main kinds of amphibolite such as diopside amphibolite, olivine diopside amphibolite, feldspa- thic amphibolite and amphibolite etc, diopside mpahibolite is the leading and most important kind. In the past the cause of the forma ion of amphibolite in this district was thought to be the products of crystallization of differentiation of basic and intermediate magmas. After conscien tiously researching both in the field and in the laboratory the present writer puts forward the theory that amphibolite in the district is the result of" assimilation-contam- ination-metasomatism".