Zircon SHRIMP U-Pb age of Yanyaozhai Subvolcanics from the Southern Margin of the North China Craton is 1781±12 Ma. Yanyaozhai Subvolcanics consist of alkaline trachyte-toscanite,dacite,rhyolite. Its SiO2 content is in the range of 59.30%～72.33%. The rocks belong to mid-acidite with over-saturated aluminum, characterized by the enrichment of alkaline, and high K and low Ca,Mg,Sr and high Ga、Zr、Nb、Ce、Y content, and similar to A-type granite. The rocks are characterized by strongly heavy REE depletion, fractionated REE patterns, and predominantly weakly negative Eu anomalies although weakly positive Eu anomalies in some samples. As for trace element features, the rocks are characterized by enrichment of large-ion lithophile elements and relative depletion of the high field strength elements. The 176Hf/177Hf ratios are between 0.281415 and 0.281557, and εHf(t) values are -11.663~-5.977, with mean value is -8.657; the initial ratios of 143Nd/144Nd are 0.5095~0.5099, and the mean εNd(t) value is -11.37. All these results suggest that the tectonic environment of Yanyaozhai subvolcanics belongs to the post-collison extensional type, and indicate the magma source region is deep and related to the enriched lithospheric mantle and underwent contamination of crustal components.