Abstract: A mount of straw residue left in the field is able to raise the environmental pollution and resource waste. Utilization of the straw resource enables to resolve these problems, promote the economic growth, open the new industries and increase employment. The manufacture of biodegradable film raises the high utilization value of soybean straw resources. The biodegradable film is low cost and friend environment, which can meet the requirements of covering and cultivation. The method applied five factors and five levels 1/ 2 quadratic regression orthogonal rotation center. Grammage, mixing ratio, rosin, bauxite, and wet strength agent were influencing factors. Dry tensile strength, wet tensile strength were objective functions. The measurement of dry tensile strength was referenced to the GB/T453-1989 and the measurement of wet tensile strength was referenced to the GB/T465.2-1989. This paper analyzed the effect of factors on the dry tensile strength and wet tensile strength, the rate of factors on objective function, and the optimal technology parameters of soybean straw fiber for manufacturing biodegradable mulch. Through the analysis of the effect of factors on function, the models of dry tensile strength and wet tensile strength were built and the models were significantly different. The rank of effect of every factor on functions was judged by the F value. The results showed that 1)The rank of effect of five factors on dry tensile strength: KP mixture ratio, grammage, wet strength agent, rosin and bauxite; 2)The rank of effect of five factors on the wet tensile: KP mixing ratio, grammage, wet strength agent, bauxite and rosin; 3)in the conditions when grammage of 50-110 g/m2, mixing ratio of 0-50%, wet strength agent of 1.2%-2.0%, rosin of 0.3%-1.5%, bauxite of 1%-5%, optimal technology parameters of soybean straw fiber manufacturing biodegradable film were grammage of 92-110 g/m2, mixing ratio of 23.3%-30%, wet strength agent of 1.2%, rosin of 0.3% , bauxite of 5%, assuming the dry tensile strength is greater than 30 N and wet tensile strength is greater than 15 N.