Abstract: This paper studies the effects of subalpine coniferous forest degradation caused by dwarf bamboo expansion on soil K and Mg contents. We used community diversity indexes, soil pH, soil organic matter and the contents of N, K and Mg in litter and soil to compare among primary subalpine coniferous forest (PF), mixed broadleaf-conifer forest (SF) and dwarf bamboo bush (BB). In addition, stepwise regression was used to explore the main factors affecting soil K and Mg contents. The results showed that: (1) plant numbers in tree and shrub layers, species richness and diversity indexes decreased significantly with forest degradation; (2) the contents of TNlitter, TKlitter and TMglitter displayed significant differences among the three degradation levels, which was highest in PF, and lowest in BB; (3) with the forest degraded to bamboo bush stage, SOM, TNsoil, ANsoil, TKsoil, AKsoil and TMgsoil significantly decreased; (4) stepwise regression analysis showed that TNsoil contributed 57.0% and 68.0% to TKsoil and AKsoil, respectively, SOM contributed 35.9% to AKsoil, and ANsoil contributed 47.1% to TMgsoil, indicating that soil N and SOM content were the main factors affecting soil K and Mg contents, followed by community diversity. Our results proposed that the degradation of subalpine coniferous forest caused by dwarf bamboo expansion not only reduced soil C and N content, but also led to soil K and Mg loss.