waterlogging damage is the main obstacle factor of agriculture in plain and lake region. In this paper, the standard of waterlogging damage is suggested based on the definition of waterlogging, with a lot of observational data in Jianghan Plain, and the cause and process of waterlogging formation are discussed. The conclusions are as follows.1. The waterlogging damage is taken piece if the buried depth of groundwatcr in dry season is less than 0.6m, and the standard of waterlogging damage can be divided into six degrees. (1) Non waterlogging, the buried depth of groundwater is more than 0.6m; (2) Marginal waterlogging, the groundwater level is 0.3-0.6m; (3) Slight waterlogging, the groundwater level is 0.2-0.3m;(4) Mid waterlogging, the groundwater level is 0.1-0.3m; (5)Hard waterlogging, the ground water level is within 0.1m; (6) Very hard waterlogging, the still water is On the ground surface.2. the trigger mechanism of waterloggia;damage is the coupling of leading factors such as the surface water dynamic, the groundwater dynamic, the micro-landforms, the reclamation and cultivation of the wetland, and the cropping system.3. The mechanism of waterlogging damage can be presented as follows. In natural situation, the living factors of environment (inducing human activities) are disastrously coupled to change the payare ochemical properties of sod,and then to influence the growtg of crops.At last it results in decrease ot the crop product.