Abstract: In order to improve the intracellular polysaccharide yield of Agaricus blazeimurill, chemical mutagenesis method was applied to treat Agaricus blazei strains. A high yield mutant, named ABM48 was obtained with polysaccharide content 12%, which was increased by 36% than the original strain. The acute toxicity and subacute toxicity experiments showed that this mutant was safe and non-toxic. It had broad application prospects in the edible and medicinal area.