The Mesozoic volcanic rocks玩western Liaoning Province which include those of the Xinglonggou cycle, the Lanqi cycle and the Yixian cycle, are mainly distributed in the Yarn-liao platformal fold belt. These rocks chaia- cterized by having SiO2 of 60.2% (average)，staiad.ard alumina and high Na20 content plot inn the range between the alkali-lime series and the weak- alkali series. In addition, their REE total.contents(∑ REE+Y) and europium negative anomaly are lower ahd Isr is from 0 .70546 to 0.70653. From the petrochemical point of view, these rocks are. similar the Archean metamor- phic rocks of the Jianping Group, which are their basement and source area. So it can be said that there is a gehetic connection between them. The results calculated using the binary mixed formula proposed by G. Faure, in which the Archea,n metamorphic rocks of the Jianping Group and depleted mantle are thoughit to be the end members, show that the Mesozoic volcanic rocks in western Liaoning are derived from the metamorphic rocks of the Jianping Group (65.8% -82.1%)and depleted mahtle ( 34.2% -17. 9% ) Therefoxe, we shall come to the conclusion that the volcanic rocks were mainly formed by partial melting of source materials-the late Archean meta- morphic rocks of the Jianping Group, and belong genetically to the unmatu- red crust remelting type.