Conservation tillage has become a promising farming technology with mechanized operations as the main means. The method of minimum tillage or no tillage planting is widely adopted, where the crop straw and stubble are used to cover on the soil surface, in order to effectively reduce the soil wind erosion and water erosion, while improve the ability of soil to keep moisture and water. As a kind of conservation tillage, mulch tillage is mainly used to chop up the straw by a combined tillage machine and mix it evenly into the soil. As such, the mulch tillage can contribute to soil moisture infiltration, and high-quality seed beds. After the corn harvest in the first autumn, the full amount of straw-covered arable land was operated directly by the combined soil planter with the soft rake. In the second spring, the seed bed making machine was used to prepare the whole field of the seed bed, to build a high-quality seed bed and improve the emergence rate of corn. Most previous research focused on the effect of straw mulching and tillage methods on soil moisture infiltration performance. However, it is of great significance to explore the suitable straw returning and tillage method for soil protection in black soil area. In this study, a Design Expert software and a Box-Behnken test were used to conduct an experimental study on the infiltration performance of straw on soil moisture in black soil area in mulching tillage. In the column experiment, a quadratic regression orthogonal experiment was designed with three factors and three levels, including the depth, the quantity, and the length of mixed straw. The experimental results showed that the significant order of the influence on the amount of water seepage was as follows: the depth of mixed straw, the length of straw, the quantity of mixed straw. A response surface mathematical model was established to analyze the influence of various factors on soil moisture infiltration performance, and thereby to comprehensively optimize the influencing factors. The optimal combination was achieved, where the water seepage reached the maximum, when the depth of mixed straw was 20 cm, the quantity of mixed straw was 80%, and the length of straw was 9 cm. Using the optimized parameters for experiments, the soil water infiltration rate was up to 0.247 L. The findings can provide a sound reference for the adjustment parameters in the combined tillage machine in the mulch tillage, particularly on a theoretical support for black soil protection.