Abstract: The composite microbial system of MC1 was used to pretreat and hydrolyze corn straw in order to enhance anaerobic biogasification. The results of pretreatment and hydrolysis indicated that the pH value of the hydrolysate was as same as that of lignocellulose degradation by MC1, decreasing in the early phase and increasing in later stages of the degradation. The MC1 efficiently degraded the corn straw by nearly 59.0% during which its cellulose content decreased by 53.1%, hemicellulose content decreased by 76.4%. Total levels of various volatile products and chemical oxygen demand(COD) peaked in the fourth day after hydrolysis, and water-soluble carbohydrate peaked in the second day. Five major compounds were quantitatively analysed and the contents of each compound were ethanol 2.38 g/L, acetic acid 0.57 g/L, propanoic acid 0.11 g/L, butanoic acid 0.62 g/L and glycerine 0.22 g/L. The results of anaerobic digestion showed that the total biogas productions and the total methane productions of treated corn straw by MC1 were 33.0% and 58.1% more than the untreated ones. Accordingly, the composite microbial system pretreatment has the potential for further development and application for biogas production of corn straw.