Abstract: Using grey system theory, periodic weighting in coal mine face is regarded as a catastrophe. Following building mechanism of linear GM (1, 1) forecasting model, a non-linear GM(1,1) forecasting model in constructed in this paper. Usinga special case of non-linear model, the Verhulst model and linear model, the periodic weighting lengths under two different coal mine conditions are forecasted. The results show that for different geological conditions, different forecasting models may be used and no a single linear model can simply forecast. For situation of geological conditions approriat to a sudden change occurring, excitative forecasting model can be constructed to forecast periodic weighting length and other pressure parameters.