This　paper　aims　to　address　the　problem　of　amplified　ground　motion　at　topography　with　rock-dominated　basin.　We　selected　Wudu　basin　of　Mianyang　region　(northwestern　Sichuan　province)　as　our　study　area,　which　is　10km　from　the　rupturing　zone　of　the　2008　Wenchuan　earthquake　(Ms8.0),　and　has　suffered　strong　shaking.　Seismic　records　of　local　and　regional　aftershocks　were　used　to　provide　information　on　study　topographic　effect　on　seismic　motion　at　different　parts　in　the　Wudu　basin,　and　comparisons　of　peak　ground　acceleration　and　horizontal-to-vertical　spectral　ratio　(HVSR)　method　are　used　for　our　study.　Time　and　frequency　domain　analyses　based　on　the　aftershocks　records　show　that:　firstly,　in　general,　amplification　for　middle-fault　zone　is　a　little　higher　than　for　near-and　far-fault　zone,　and　amplification　increase　gradually　from　northern　edge　to　southern　edge　with　decreasing　elevation　from　570m　to　548m,　which　is　related　to　the　epicenter　location　and　seismic-wave　propagation　direction;　secondly,　S-wave　and　coda　experienced　amplification　factor　much　larger　than　P-wave　as　well　as　duration　for　S-wave　prolonged　due　to　interaction　between　seismic　wave　and　undulating　topography　of　the　basin.