Rock magnetism can be used to decipher the magnetic carrier materials, and it has been widely used in seismogeological research, such as the magnetic mineral change, friction temperature and earthquake slip dynamic during large earthquake. The 2008 Mw 7.9 Wenchuan Earthquake induced two major earthquake surface rupture zones, including the Yingxiu Beichuan and Guanxian Anxian earthquake surface rupture zones. The earthquake fault rocks close to the two surface rupture zones give a good chance for the rock magnetism. In this study, the fault rocks magnetic studies in the two trenches close to the two Wenchuan Earthquake surface rupture zones were used to discuss the earthquake slip dynamics, including the Bajiaomiao and Jiulong trenches along the Yingxiu Beichuan and Guanxian Anxian earthquake surface rupture zones, respectively. This study also combined with the recent rock magnetism from the earth surface and WFSD 1. The results show that: ① The rock magnetism, from the Bajiaomiao trench and other previous researches, shows that the high susceptibility of the fault gouge along the Yingxiu Beichuan earthquake fault zone was caused by the new by formed ferrimagnetic minerals, such as magnetite and hematite, so the Yingxiu Beichuan earthquake fault had experienced high temperature and rapid speed thermal pressurization earthquake slip mechanism; ② The rock magnetism from the Jiulong trench implied that the slightly low average susceptibility of fault gouge was caused by high content of Fe sulfides than that of fault breccia and Jurassic sandstones, which was possibly induced by earthquake process or earth surface process after the fault rocks exposed to the surface. If the high content of Fe sulfides was induced by earthquake process, the Guanxian Anxian earthquake had experienced the low temperature and slow speed mechanical lubrication earthquake slip mechanism; ③ The different earthquake slip mechanism was possibly controlled by the deep structure of the two earthquake faults, such as the fault occurrence. The steep dip character of the Yingxiu Beichuan fault could be easy to induce high temperature and rapid speed earthquake slip mechanism, while the low dip angle feature of the Guanxian Anxian earthquake fault could be easy to induce low temperature and slow speed earthquake slip mechanism.