The present study was conducted out at the department of nutrition and clinical nutrition ,faculty of veterinary medicine ,Sadat city university to investigate the effect of fungi (Trichoderma viridae) on the chemical composition and fiber fraction analysis of low quality roughage rice straw ((RS) (T1), bean straw (BS) (T2),mix of rice and bean straw (RBS) (T3)and wheat straw (WS) (T4).the results of proximate analysis showed that an increase in crude protein , Ether Extract and ash content in all treatment than un treated straw .CP in control are 1.95% in RS, 6.71%in BS, 4.32% in RBS,4.03 %in WS increased to 5.83%- 8.75% -8.45 -5.25% in T1,T2,T3,T4 respectively. EE in control RS,BS,RBS,WS are 1.66% -2.17%-1.7%-1.13% respectively in treatment 2.45%- 2.57 %-2.31%-1.69 % respectively.ash content in control 14.79%-9.34%-8.87%-12.78% respectively in the treatment 15.25%-10.52%-9.52%-12.95% respectively .treatment also lead to decrease in DM ,OM, crude fiber and fiber fractions (NDF,ADF).crude fiber in control RS,BS,RBS,WS are 47.05%-50.46%-47.02 %-41.35% in the treatment T1,T2,T3,T4 are 31.086%-44.79%- 33.90%- 41.22% .NDF and ADF in control are (62.91%- 39.29%)in RS,( 67.04%-46.15%) in BS,( 58.74%-41.45%) in RBS ,( 67.94%- 40.96%) in WS in treatment (54.03%-34.84%) T1,(57.43%- 36.54%)T2, (50.47%-35.93%) T3, (50.95%-38.30%)T4.,therefore we concluded from the study treatment of different type of straw lead to increase CP, EE, ash content while DM, OM, CF and NDF, ADF were decreased.