Based on study of the geological entities (core) using the Wenchuan Scientific Drilling hole (WFSD), anelastic strain recovery (ASR) stress measurements, analysis of the regional tectonic and distribution of the Wenchuan earthquake NW trending aftershocks, this study suggests that one group of NW SE structures with striking N48 °W and moderate dipping occur within the narrow range of the Yingxiu Beichuan fault. Its striking is generally parallel to the directions of Yingxiu Beichuan fault zone and the maximum main stress using AS stress measurement, and approximately perpendicular to the orientation （44°）of the maximum horizontal stress. Most of the NW SE trending structure, except several macro faulting, show more densed fractures (or hidden fractures), which are dominated by thrusting, with characteristic of locally slightly left lateral strike slip. NW SE trending fracture system on both sides of the Yingxiu Beichuan fault indicate that the Yingxiu Beichuan fault belongs to bilateral strike slip type fault, both sides of which have different formation mechanism and the opposing displacement. The vertical displacement of the Yingxiu Beichuan fault is controlled by the NE SW trending structures and the NW SE structure. The superimposed part between the NE main shock zone and NW trending aftershocks zone is of the maximum vertical displacement amount. From the analysis of time scale, during the whole process of the Wenchuan earthquake, only initial moment was expressed by strong NW SE trending thrusting, followed by movement along the faulting direction and trusting from SE to NE during the main stage of time. NW SE trending structure was the result of deep stress and energy accumulation at the Lonmenshan. When the earthquake hitting, the initial NW SE direction compression started and instantly turned to strong SW NE direction compression. NE SW trending compressional tectonic stress field was a regional tectonic stress, which was superimposed over regionally NW SE trending compressive tectonic belt due to long term accumulation and induction of the NW SE trending compression. After the earthquake, it led to the rapid transfer of seismic energy from the source region to NE direction along the fault direction and occurrences of aftershocks. Seismic energy was released eventually during the NE SW trending compressive process. Therefore, the Yingxiu Beichuan fault shows different natures at different stages of the earthquake. In the quiet period or weak shock period of an earthquake, it is characterized by thrusting in company with right lateral strike slip. But during strong earthquake period, along with the strong thrusting, it transformed into a strong right lateral slip in company with thrusting.