In this paper,the shear wave splitting features of the Longtan reservoir area are studied by adopting the traditional cross-correlation coefficient method and polarization analysis,using the data recorded by the seismic network founded by a project under the National Science and Technology Pillar Program from April 2009 to April 2010.We found that most of polarization directions at seismic stations are consistent with the direction of the overall regional stress field,but local structures and faults may control or influence the fast shear-wave polarization direction.The time-delay normalized to source-station path is between 10 to 25ms/km,and among them,the time-delay is about 10ms/km at the LIL and XIL sites,which are farther away from the dam.The water depth is relatively shallow and seismic activity relatively weak after water storage,indicating the effect of reservoir water penetration,or loading,on the state of cracks in the reservoir area.We also found that the delay time changes consistently with the water level at stations DPD and GAL.It may be related to crack expansion and water penetration caused by the reservoir impoundment. In this paper, the shear wave splitting features of the Longtan reservoir area are studied by adopting the traditional cross-correlation coefficient method and polarization analysis, using the data recorded by the seismic network by a project under the National Science and Technology Pillar Program from April 2009 to April 2010.We found that most of polarization directions at seismic stations are consistent with the direction of the overall regional stress field, but local structures and faults may control or influence the fast shear-wave polarization direction. to source-station path is between 10 to 25ms / km, and among them, the time-delay is about 10ms / km at the LIL and XIL sites, which are farther away from the dam. The water depth is relatively shallow and seismic activity relatively weak after water storage, indicating the effect of reservoir water penetration, or loading, on the state of cracks in the reservoir area. We also found that the delay time changes consistently with the water level at stations DPD and GAL. It may be related to crack expansion and water penetration caused by the reservoir impoundment.