Abstract: In order to investigate the effect of γ-aminobutyric acid(GABA)treatment on cell wall metabolism and lignification of Agaricus bisporus,the effects of 5 mmol/L GABA treatment on chitin,cellulose,lignin contents,cell wall metabolism and lignin synthesis of A. bisporus were studied(storaged at 4℃ for 12 d). The results showed that GABA treatment could significantly(P<0.05)inhibit the activities of chitinase and cellulose,and slow down the degradation of chitin and cellulose in A. bisporus,indicating that GABA treatment could maintain the structure of cell membrane and resist pressure. After 6 d storage,the lignin contents increased dramatically,and the degree of lignification was improved. The correlation analysis showed that the lignin contents was negatively correlated with phenylalanine ammonia lyase(PAL)activity(P<0.01)and positively correlated with cinnamyl alcohol dehydrogenase(CAD)activity(P<0.01). The lignin contents of GABA treatment group was lower than that of control group,and the activities of PAL and CAD were higher and lower than that of control group,respectively,which indicated that GABA could reduce the lignin accumulation of A. bisporus by increasing PAL activity and inhibiting CAD activity,and then delayed its lignification process.