The effect of pH on degradation of paper by some fungi, which able to degrade cellulose, was investigated. Trichoderma koningii, Aspergillus nigerand Penicillium nigulosum were cultured at $28^{circ}C$ for 16 days in the selective medium (PH3, PH4, PH5, PH6, PH7, PH8, PH9, PH10, PHC) containing paper as substrate. Each paper was pretreated with each pH buffer (pH 3∼pH 10, D.W.)prior to addition to the selective medium. Enzyme activities in the each culture medium were measured spectroph to metrically using C.M.C., Avicel, PNPG as the substrates for endoglucanase, exoglucanase and $eta$-glucosidase, respectively. In all experimental fungi, the enzyme activities of PH3 and PH9 medium were usually much higher than those of other experimental groups. However in the PH6medium, enzyme activity was lower than other groups. To analyze the concentration and pattern of protein in the each culture medium, the medium was concentrated by lyophilization. The protein concentration of PH3 and PH9 medium were relatively high (T.koningii; 6.31mg, 6,19mg, A.niger; 1.62mg, 1.96mg, P.nigulosum;2.50mg, 2.73mg, respectively), but that of PH6 was relatively low. The protein pattern of each medium was analyzed by using SDS-PAGE and VDS Image Master Analysis Program. The concentrations of bands in the each lane were usually high at lane2 (PH3) and lane8 (PH9) and low at lane5 (PH6). Therefore, the incresed cellulolytic activity of fungus against acidified paper could be result of structural change and deterioration of paper caused by being acidified.