The work aims to study the optimal technological conditions for extraction of polysaccharides from white asparagus scraps processing waste pretreated by steam explosion and analyze the effects steam explosion pretreatment on yield of polysaccharides. With white asparagus scraps processing waste as raw materials, the polysaccharides were extracted by steam explosion pretreatment to discuss the effects of particle size, steam explosion pressure, steam explosion time and material cavity ratio on the yield of polysaccharides. The optimal extraction process response of polysaccharide from white asparagus processing waste was designed and optimized by response surface optimization. The results showed that the effect of steam explosion pressure on the yield of polysaccharides was the biggest, followed by the particle size, steam explosion time and material cavity ratio. The optimal extraction conditions of steam explosion pretreatment were material size of 30 meshes, steam explosion time of 128 s, steam explosion pressure of 1.50 MPa. Under this condition, the yield of polysaccharides reached 8.86%, which was 22.88% higher than that of direct hot water extraction. The results show that steam explosion pretreatment has a certain promoting effect on improving the yield of polysaccharides.