Systematic research methods including mineralogy, petrology and geochemistry were used to study the Indosinian alkaline intrusions in Yinshan area. It is concluded that the Indosinian alkaline intrusions in Yinshan area make up two nearly EW_striking rock belts lying in the north and in the south respectively. The southern belt is mainly composed of augite_aegirine syenites, whereas the northern one consists mainly of alkali_syenite. Both belts are enriched in LREE, large-ion lithophile elements and high charge density elements. However, the content of compatible elements such as Cr and Ni are very low. Combined with the isotopic characteristics of Nd, Sr, and Pb, the authors have drawn the conclusion that the Indosinian alkaline intrusions of Yinshan area were generated from the enriched mantal, and during their invasion they were contaminated by crustal materials in different degrees.