The effects of boiling and microwaving on nutritional compositions, antioxidant components and antioxidant activities of fresh and frozen A. blazei Murril (AbM) were evaluated and compared. The results showed that the contents of crude protein, ash, total soluble protein, total soluble sugar, vitamin C, and total phenolics decreased by both cooking treatments, but no significant changes were observed in lipids. Amino acid composition analysis showed that the ratio of total essential amino acids to total amino acids increased, and the ratio of total non-essential amino acids to total amino acids thus decreased by both cooking treatments. Boiling and microwaving significantly decreased the contents of glucose, galactose and mannose, and the effect of boiling was higher than that of microwaving. Furthermore, boiling and microwaving significantly decreased the DPPH-scavenging activity and reducing power of AbM. Analysis of the relations between the antioxidant activities and total phenolic concentrations testified that the cooking treatments not only decreased the total phenolic contents, but also changed the types and relative amounts of phenolic compounds of AbM.