Abstract: this paper firstly expounds the concept of city overall strength.Moreover, using the method of principal component analysis(PCA)the paper comes up with the respective mainelements of 50 coalminging cities.The research results demonstrate that there are significant differences between the overall strengths of different types of coalmining citees.The ordinal sequences are: petroleum type>overall type>metallurgy type>coal type.With the diminishing of the size of city, the overall strength decreases accordingly.Furthermore, the gaps of overall strengths between large-and medium-sized cities are quite obvious as well.