Gas slip effect in porous media in the slip flow regime is very important in various scientific and engineering fields. It has been shown that gas slippage factor plays an important role in determination of gas apparent permeability. In this work, a novel predictive model for gas slippage factor in microporous media with low permeability in the slip flow regime is developed based on the fractal theory. Every parameter in the proposed model has clear physical meaning. The predictions of gas slippage factor by the proposed model show the same variation trend with the available experimental data. Based on the proposed gas slippage factor, it is found the ratio of the gas permeability to the intrinsic/liquid permeability under mean pressure has the same variation trend with empirical correlations. The effects of structural parameters of porous media on the gas slip factor are discussed in detail. (C) 2012 Elsevier Ltd. All rights reserved.