Straw magnesium oxychloride cement composite material(SMOCC, hereinafter referred to as straw composites) was prepared using straw as a filler, magnesium oxychloride cement as binder, with an appropriate proportion ofmineral admixture and additives added by press process. First the effect of straw type, length, moisture content(by mass,the same below) on material properties was studied, then through orthogonal experiment the influences of three factors of straw content, magnesium oxychloride cement content and sand content on compressive strength were investigated. The relationship between dry density and compressive strength was studied by the optimal formula. The results show that: under the conditions of straw moisture content ≤10%, magnesium chloride solution at 23 °Bé, and conservation for 28days, with the same ratio of binder and adopted pressure locked process, different straw types have little effect on compressive strength; with the change of straw length, the addition of wheat straw is more stable than that of corn straw, and the compressive strength of the material is the highest when the straw length is 100mm; the influence of the three factors on the compressive strength of the material is: cementing material ratio,straw content,sand content; within a certain range, the compressive strength of straw composites increases linearly with the increase of dry density.