The term beta diversity was first introduced by Whittaker in 1960. It is described as variation of the species composition of assemblages. Beta diversity can be partitioned into two antithetic components, that is spatial species turnover and nestedness of species assemblages. Identifying those two components of beta diversity is an important task for revealing the mechanisms of community assembly. Some studies have been performed to disentangle the spatial species turnower and nestedness for communities in aboveground ecosystems, however, beta diversity of assemblages in belowground ecosystems is still unclear. The objective of this study is revealing the beta diversity of ground beetle assemblages and then partitioning the beta diversity into spatial species trunover and nestedness of species assemblages. Field experiments were carried out using pitfall traps in two broad-leaved Korean pine (Pinus koraiensis) mixed forests in Liangshui and Fenglin nature reserves, respectively, Xiaoxing'an Mountains, Northeast China. We collected ground beetles in a 9 hm² plots (300 m×300 m) by regular sampling method in August, October in Liangshui plot. We captured ground beetles in a 9 hm² plot (300 m×300 m) with the same method in August, October in Fenglin plot. There were 450 traps in Liangshui and Fenlin plots in total, respectively. We identified beetles into species level. We analyzed Carabidae, Staphylinidae and Silphidae beetles because their dominance in richness and abundance in each plot. We evaluated beta diversity based on PERMDISP2 method. We partitioned total beta diversity into spatial species turnover and nestedness of species assemblages. In total, 39 species and 856 individuals were captured in Liangshui plot. Forty-three species and 1182 individuals were collected in Fenglin plot. Results of diversity analysis showed that (1) Significantly higher species richness and abundance of entire beetle assemblages (total beetles of those three families) were detected in August in Liangshui plot. While significantly higher species richness and abundance of entire beetle assemblages were detected in October in Fenglin plot. The distribution of species richness and abundance for each Carabidae, Staphylinidae, Silphidae assemblages in Liangshui and Fenglin plots were family dependent. (2) There were no significant differences of beta diversities in ground beetle assemblages between Liangshui and Fenglin plots, except for Carabidae and Silphidae assemblages in August. (3) Beta diversity patterns for entire ground beetle assemblage and each family beetle assemblage were almost completely caused by spatial species turnover in Liangshui and Fenglin plots, while the contributions of nestedness of species assemblage were small. It suggested that beta diversities of ground beetle assemblages were mainly structured by spatial species replacement but not by species loss, suggesting a high proportion of endemics present in the two mixed forests. In this study, we suggested that spatial species turnover is the most important component for beta diversity in broad-leaved Korean pine mixed forest, therefore a more important role of spatial species turnover should be considered for understanding the mechanisms driving ground beetle assemblages in broad-leaved Korean pine mixed forest. This study provides scientific foundation for revealing the mechanisms of community assembly in soil animal community.