Straw mulch mat is a promising alternative to petroleum-based plastic mulching film. The straw pretreatment process parameters influence the mechanical properties of the mat. To explore the effect of pretreatment process parameters on physical properties of wheat straw mulch mat, a five-factor and five-level central composite design (CCD) methodology was studied. With response surface methodology (RSM) analysis, the effects of parameters (soaking water temperature, soaking time, processing speed, manufacturing temperature, and manufacturing pressure) on dry tensile index and wet tensile index of original film, and initial beating degree of the straw pulp were reported. The optimal technical parameters were optimized as soaking water temperature 90 °C, soaking time 1.5 h, manufacturing pressure 1.5 MPa, processing speed 83.5 to 87.8 r/min, and manufacturing temperature 95 to 100 °C. With the optimal condition, the dry tensile index, wet tensile index, and initial beating degree were higher than 8 N·m/g, 4 N·m/g, and 17 °SR, respectively. With this pretreatment of raw materials, the wheat straw mulch mat would meet the demands of mechanical properties for agriculture mulching after adding chemical additives.