Abstract: Mesozoic volcanic rocks are widely distributed in Western Liaoning Province. They can be mainly divided into three eruption cycles, i.e. the Xinglonggou, the Lanqi and the Yixian cycles, among which the Yixian cycle is most importantly developed. Based on a high precision sampling on Yixian cycle, this paper made a particular study on the geochemical characteristics of trace elements in volcanic rocks of Yixian cycle. We found that all volcanic rocks in Yixian cycle were derived from a common source, which seems to be an admixture of crust and mantle materia1s. All of them were formed through several eruption pulses in a prolonged geodynamic process. Each eruption cycle had pulsation character and the, volcanic activity weakened gradually. The variation of trace element parameters shows a quite coincidence with the lithology and eruption cycle subdivision, and provides a sensitive indicator on volcanic activities. This paper also discusses the structure background of Yixian volcanic cycle. which should be affected by the lithosphere delamination at K3-J1 in this area.