Feature selection algorithm plays an important role in text categorization. Considering some drawbacks proposed from traditional and recently improved information gain (IG) approach, an improved IG feature selection method based on relative document frequency distribution is proposed, which combines reducing the impact of unbalanced data sets and low-frequency characteristics, the frequency distribution of features within category and the relative frequency document distribution of features among different categories. The experimental results of NLPCC-ICCPOL 2016 stance detection in Chinese mi...