Gubaoquan intrusion lies in southern of Beishan rift zone , Gansu province. it covers an area of 1.7km2 in shape of stock, and mainly consists of hornblende gabbros ,including lots of olivine gabbros, pyroxene troctolites , and show gradual transition relation each other. Most of samples belong to tholeiite series, only a few sample belongs to alkali series. All kinds of rocks have very low TiO2，Na2O，P2O5 content and LILE, REEs(∑REE＝5.29×10-6-17.30×10-6). Theirs εNd(t)=+6.9～+8.1, εSr(t)=+2.3～+17.4, 206Pb/204Pb=18.463～18.645, 207Pb/204Pb=15.604～15.634, 208Pb/204Pb=38.351～38.497 respectively. The magma source is depleted mantle by previous melt extraction, and the magma experienced contamination to some extent. The primary magma is enriched ferruginous. The main dark-colored minerals are clinopyxene and olivine in the processes of the fractional crystallization and plagioclase accumulate. Gubaoquan intrusion is the product of highly partial melting of spinel peridotite at low pressure level in mantle.