Abstract: In order to master a distribution law of the water flow crack zone in the overburden strata after a seam mining,a FLAC finite difference program was applied to analyze the stress variation above the goaf with different mining width. According to the Mohr- Coulomb criterion,a distance from the mining top boundary to the highest point of the single element stress yield zone in the model would be the height of the water flow crack zone. A FLAC model was established as the first coal mining face of a mine to simulate the water flow crack distribution under the condition of different mining width. The results showed that with the advancing of the coal mining face,the water flow crack zone would be in a flat arch firstly and would be in a saddle- shape lately. The height of the water flow crack zone at the initial period would be increased with th e width of the coal mining face increased and would not be increased when the width of the coal mining face was over a critical value. The simulated height of the water flo W crack zone was ftted with the actual measured height. The regression analysis showed that under the condition of the same mining thickness,the height of the water flow crack zone and the mining width would be in a quadratic function relationship.