Comparative statistical analysis of morphology of Mesobuthus martensii and Mesobuthus eupeus (Scorpiones: Buthidae) indicated highly significant differences between these two species. Mann-Whitney U test showed that: except Ca_L/AW, Ca_AW/PW and Met-V_L/H in female, Ca_AW/PW and Met-V_L/H in male, all morphometric ratios demonstrated significant differences between M. martensii and M. eupeus. Principal component analysis (PCA) showed that M. martensii and M. eupeus are clearly different species in morphology. Three statistical analyses (Kruskal-Wallis one-way ANOVA, PCA and cluster analysis) were applied to M.martensii from 27 confirmed localities in five provinces of northern China. The results suggested that: (a) Although M. martensii is common and widespread in northern China, its morphology does not vary significantly, but there is more variation in females than males, and the variation both in males and females is below species level; (b) the populations from Hebei, Ningxia, Inner Mongolia, and Liaoning Provinces were similar to each other while the populations from Qinghai were separated from the others; (c) except Met-I_L/W and Met-V_L/W, each ratio of metasoma in both females and males of Qinghai populations was smaller and the ratio of Ca_L/AW was larger than those from other provinces.