[Objectives] Determining the elevational distribution of species diversity along altitudinal gradients is of critical importance in biodiversity and conservation research, the hump-shaped pattern of species diversity is the most common one. To understand the species diversity distribution pattern of Taibai Mountain, and to provide basic data and references for the study of elevational biodiversity gradient patterns. [Methods] We surveyed the diversity of small mammals along the elevational gradient on the northern slope of Taibai Mountain from June to September in 2020 and 2021. The elevation range of the study was 780﹣3 767.2 m, with a gradient of 200 m. Fifteen sampling points were set, with a total of 4 150 rat traps, 105 traps and 8 sample sites. Four diversity indices (Shannon-Wiener, Margalef, Simpson, Pielou) were used to compare the diversity discrepancy between different elevational forest types and used to reveal the diversity distribution pattern. All species diversity index calculation, cluster analysis was completed in SPSS 21.0 and R language. [Results] Our study surveyed totally 148 individuals representing 21 species that were belong to 12 genera, 7 families and 4 orders. The species diversity of Quercus variabilis and Q. aliena which in the middle altitude area was the highest, and that of Abies fargesii in high altitude area was the lowest. The elevational distribution pattern of species diversity of small mammals in the northern slope of Taibai Mountain Nature Reserve is a left-biased mid-peak pattern. The two non-parametric estimations of species richness Chao2 and Jackknife2 indicate that increased sampling intensity is still needed in Betula albosinensis. [Conclusion] The species diversity of small mammals in broad-leaved forest was generally higher than that in coniferous forest. This distribution pattern was mainly related to the composition of Oriental fauna and Palaearctic fauna, endemic species and non-endemic species of small and medium-sized mammals in the community. The mountain range-valley landform on the northern slope of Taibai Mountain provides favorable conditions for the diffusion and migration of northern and southern species. The climate and geographical characteristics in the valley were similar, forming a typical elevational vegetation zone, which made the distribution of species diversity of small mammals had similar characteristics.