[Objective] To clarify the effects of biochar application rate and irrigation volume on the salt reduction in sodic saline soil of the Yellow River Delta and to identify the optimal ratio between the two. [Methods] A twofactor five-level orthogonal rotation combination design was employed in soil column experiments to simulate the effects of irrigation volume（1.00, 1.07, 1.25, 1.43 and 1.50 times the saturated soil moisture content, θ_s） and biochar application rates（1.00%, 1.59%, 3.00%, 4.41% and 5.00% of soil mass in the 0～20 cm layer, S_w） on soil volumetric moisture content, electrical conductivity, pH, and ion mass fraction in sodic saline soil. The optimal water-biochar combination ratio was determined using the analytic hierarchy process and multiple regression equations. [Results] 1) The treatment with 4.41% S_w and 1.43 θ_s achieved the highest soil volumetric moisture content（31.71%） and pH（8.50）. In contrast, the treatment with 3.00% S_w and 1.25 θ_s showed the most significant reductions（p＜0.05） in electrical conductivity, Na+ mass fraction, and sodium adsorption ratio（SAR） compared to the untreated soil, with decreases of 82.05%, 89.71% and 86.43%, respectively. 2) Both water and biochar synergistically affected the comprehensive evaluation index of salt reduction effect in sodic saline soil, with irrigation having greater influence than biochar application. The comprehensive evaluation index initially increased but subsequently decreased with the increasing application rates of both factors. The maximum evaluation index（0.72） for salt reduction in sodic saline soil was obtained at an irrigation level of 1.37 θ_s combined with a biochar application rate of 3.45% S_w. [Conclusion] To enhance sodic saline soil quality in the Yellow River Delta, the synergistic combination of 3.45% S_w biochar application and 1.37 θ_s irrigation is the most effective strategy for salt reduction in saline-alkali soil. The research results provide a theoretical basis for saline-alkali soil remediation.