Abstract: Extreme flood is characterized with low frequency but large affecting area and huge economic loss. The natural and social attributions of extreme flood disaster were analyzed in the paper. The current assessment methods are mainly used for common frequently-occurred flood, but not suitable for extreme flood.The spatial information grid of hydrological characteristics and social economic attribution for extreme flood were constructed through referencing the spatial information technology. In further, the spatial information grid model of extreme flood losses was established with the spatial topological relationship of different grid information. The model can not only reflect the spatial characteristics of extreme flood, but also assess the losses of extreme flood through combining relevant database. The model was employed to assess the direct economic loss in main city district north to Songhuajiang River in Harbin City, which indicates the model is feasible in practice for extreme flood disaster losses assessment.