The invention discloses a method for detecting fungi polysaccharide. The method organically integrates MALS, high-response differential method, and DLS to carry out online, offline, and quantitative detection, with monophase chromatographic technique as core, thus, the characteristics of polysaccharide, like absolute molecular weight, dispersion degree, molecular conformation, dissolubility, and stability, can be represented and analyzed. The method comprises preparation of sample, preparation of mobile phase, sample injection, buffering, focusing balancing, elution and separation, detection,and the like. Compared with prior phenol-sulfuric acid method, gel electrophoresis method, and HPLC method, the invention has the advantages that quantitative detection and qualitative detection are integrated; the sample is not damaged through whole physical detection; the sample adsorption quantity is little; the operation is simple and rapid, and the condition is mild; the absolute molecular weight and the distribution thereof of the polysaccharide can be obtained without standard sample; the sensitivity is high and can reach 10<-9>; and the physicochemical characteristics of polysaccharide can be simultaneously detected. The invention can be widely applicable to analysis detection, quality control, research and development of polysaccharide and other related compounds.