Abstract: In order to increase the yield of soluble polysaccharides, the fruit body of Ganoderma lucidum was subjected to twinscrew extrusion before hot-water extraction.The solid-liquid ratio, rotary speed and barrel temperature of screw were optimized through single factor and orthogonal experiment according to the yield of soluble polysaccharides.The comparison between screw effects on polysaccharides molecular weight distribution were carried out using high performance size exclusion chromatography coupled with multiangle laser light scattering ( SEC-MALLS/RID) .When the particle diameter was 60 mesh, the optimum conditions were as follows, the barrel temperature 160 ℃, solid-liquid ratio 1 : 3, rotary speed of screw 150 r/min. Under this condition, the yield of soluble polysaccharides was 92.7% higher than before, reached 7.92%.It means that the yield of soluble Ganderma lucidum polysaccharides can be increased by twin-screw extrusion to a great extent, and the ratio of low-molecular weight polysaccharides increased after twin-screw extrusion.