Aims <p>To evaluate the effects of biochar produced at different pyrolysis temperatures on soil quality and its regulatory factors, and to elucidate the relationship between soil quality and potato yield, thereby identifying the optimal pyrolysis temperature and better biochar rates.</p> Methods <p>A two-year (2023–2024) randomized block field experiment was conducted in North China to investigate the impact of different biochar pyrolysis temperatures (T1: 300 °C, T2: 500 °C, T3: 700 °C) and application rates (C1: 10 t·ha⁻1, C2: 20 t·ha⁻1, C3: 30 t·ha⁻1) on soil quality and its synergistic effect on potato yield.</p> Results <p>(1) The Soil Quality Index (SQI) calculated using the nonlinear scoring model more accurately assessed soil quality in potato farmland, with the C2T2 treatment achieving the highest SQI, showing an increase of 1.04 to 1.28 times compared to other treatments over the two years. (2) In 2023 and 2024, the potato yield under the C2T2 treatment increased by 23.93% and 30.69%, respectively, compared to CK, and potato yield exhibited a linear increase with rising SQI. (3) Partial Least Squares Path Modeling (PLSPM) analysis indicated that the improvement in SQI was mainly attributed to biochar-enhanced soil moisture (θ), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and organic carbon content (SOC), which in turn promoted potato yield.</p> Conclusions <p>A soil quality evaluation method is developed for a sandy loam soil used for potato production in an arid region., The suitable biochar application effectively improved θ, MBC, MBN, and SOC, thereby synergistically enhancing soil quality and potato yield.</p>