Discretization is one of the important components of the data preprocessing. Discretization can turn numeric attributes into discrete ones. There are many different kinds of discretization methods. This paper describes the Chi2 algorithm which is a simple and general discretization algorithm. In this algorithm, the \chi^2 statistic value is used as an evaluative standard to discretize the numeric attributes. However, the Chi2 algorithm dose not consider the sequence of discretization for each attribute in the second phase. And the inconsistency rate cannot fully reflect the characteristic of dataset. These drawbacks will affect the result of discretization finally. In this paper, some concepts of the rough set are introduced to improve the Chi2 algorithm.