Clarifying the driving factors of post-fire soil physicochemical properties is an important part of explaining ecosystem response to fire disturbance. This study aimed to analyze the determinants of post-fire soil physicochemical properties in Dahurian larch forests, to gain an in-depth understanding of the role of fire disturbance in boreal forest ecosystems, and to provide scientific support and theoretical basis for boreal forest post-fire recovery and sustainable development. The research object was one-year-post-fire Dahurian larch forest in the Greater Khingan Mountains. A total of 35 burned and unburned plots with different fire severity and site conditions were established. In each plot, species, diameter at breast height (DBH), survival status and other arbor data were recorded, and terrain data such as slope aspect, slope position, slope gradient, and altitude were measured, and the fire severity was quantified through vegetation changes. Nine physical and chemical indicators of the collected soil samples from two layers (0-5 and 5-10 cm) were measured, and the differences of these indicators were compared between the burned and unburned plots. Then, the correlation of quantitative results of fire severity and each index were analyzed, and the effects of fire severity, topography and arbor on the soil physicochemical properties in the burned area were compared. Compared with the unburned plots, fire disturbance enhanced the dispersion of soil physical and chemical indexes, significantly (P<0.05) increased total nitrogen (TN), total organic carbon (TOC) content in 5-10 cm soil and both two layers' soil moisture content (MC). There were few soil physicochemical indexes obviously correlated with fire severity. The soil MC in 0-5 cm was observed to decrease with the increase of fire severity index. Available potassium (AK), pH and ammonium nitrogen (NH₄⁺-N) of 5-10 cm soil and inorganic nitrogen of 0-5 cm soil increased with the increase of fire severity index. Correlation analysis showed that topographic factors were highly correlated with soil physicochemical properties in the burned area. Slope position, slope gradient, and slope aspect were significantly negatively correlated with TN and TOC of 5-10 cm soil and hygroscopic water content (HMC), MC, nitrate nitrogen (NO₃^--N) (P<0.05), while they were mainly positively correlated with AK, pH, NH₄⁺-N, and available phosphorus (AP), among which the slope gradient were highly significant (P<0.01) positively correlated with AK, pH, NH₄⁺-N and AP of 0-5 cm soil. The variance partitioning analysis (VPA) results showed that the variation of soil physical and chemical indicators in the unburned plots was mainly explained by the sharing of arbor and topographic factors. However, in the burned area, the explained proportion of arbor factors decreased, while the individually explained proportion of topographic factors increased, which resulted in the sharing proportion was greatly reduced. Fire disturbance could enhance the impact of topography on soil properties. Topography was a dominant factor for the differences in soil physicochemical properties in the burned areas, and its impact was more profound than fire severity, so the ecosystem response to fire disturbance depended not only on fire severity. Therefore, the dominant role of topography may be one of the important reasons for the different results and conclusions drawn from the studies on the relationship between fire severity and soil physicochemical properties in different regions.