This paper gives a description of the co-seismic and post-seismic groundwater level changes induced in Chinese mainland by the 2011 Mw9.0 Japan earthquake,and the corresponding stress changes calculated on the assumption of linear elasticity.The result shows that the main types of changes were oscillations and step increases.The North-South Seismic Belt and the Shanxi Seismic Belt were the main areas affected by the earthquake.