Abstract: On March 11^th, 2011, an earthquake with magnitude of M_w 9.0 occurred off the Pacific Coast of Tohoku, and triggered widespread liquefaction in Tohoku and Kanto regions of Japan. Based on the field investigation and data analysis, the characteristics of liquefaction, liquefaction-induced damages, different failure mechanisms, characteristics of re-liquefaction in the aftershocks and seismic tsunami hazards are presented. The study also shows that re-liquefaction resistance is greatly affected by the intensity of earthquakes, stress history and dissipation of excess pore-water pressure. The damage process due to the seismic tsunami hazards is divided into three stages, the post-earthquake liquefaction stage, the recovery stage of soil strength and the flow-sliding failure stage. Finally, the effectiveness of ground improvement methods (sand compaction pile and sand drain method) in this massive earthquake is summarized for liquefaction mitigation in the future.