A biological pretreatment with Trichoderma reesei culture was used to pretreat straw wastes (i.e. rice straw, wheat stalk and their mixture) at ambient temperature (30±1)℃ to improve their biodegradability and anaerobic biogas production. The initial Trichoderma reesei spores dose was 200μL, it had twice expanding training, and the pretreatment time of 72h was appropriate for biological pretreatment. These treatment conditions resulted in more total biogas yield, methane yield and shorter technical digestion time compared with the untreated sample. The total gas production from pretreated straw wastes reached the maximum of 14555, 15103 and 17130mL for rice straw, wheat straw and their mixture, respectively. The average methane concentration levels were at 48.2%, 45.4% and 47.8%, respectively. The highest methane concentrations were at 60.5%, 66.1% and 66.8%, respectively. The average methane concentrations were increased by 205.1%, 213.1% and 214.5% compared with the untreated sample. The values of pH, VFA were located in normal range. The average daily degradation values of COD reached 522.23, 542.50 and 668.72g/d and TS degradative rates were 172.84, 183.12 and 205.54mL/g, respectively. The digestion time DT90 for pretreated straw waste which contained a mixture of rice straw and wheat stalk was calculated. The significant reduction of digestion time indicated that the straw had become more accessible and readily biodegradable after biological pretreatment.