Through the analysis of mould steel from different sources by the original position statistic distribution analysis (OPA), new information on the position, state and content distribution of each chemical component in the cross section of mould steel was obtained in a relatively wide range. As a result, the differences among the parameters of mould steel from different sources were uantitatively characterized, including the biggest segregation, the statistic degree of segregation, statistic degree of accord with contents (statistic degree of homogeneity), the statistic density as well as the content, variety and statistic size distribution of the inclusions. The experimental results could be used as reference for analyzing the quality variance of mould steel from different sources.