Delignification is crucial in the energy utilization process of lignocellulose materials. In this study, efficiency of biological pretreatment of corn straw using different carriers of precolonized fungis, including Trametes versicolor, Trichoderma chromospermum, Trichoderma atroviride and combined fungi (T. versicolor + T. chromospermum, T. versicolor + T. atroviride) was investigated under unsterilized condition. Results showed that nearly negligible lignin degraded in the process of direct fungal pretreatment of unsterilized corn straw within 30d. It seems that inoculum of fungi cannot compete to the indigenous microorganisms of unsterilized corn straw, resulting in low lignin degradation rate. However, the degradation rates of 34.0%, 38.1%, 38.1%, 39.1% and 40.3% lignin in the sterilized corn straw were observed after 30d of cultivation by T. versicolor, T. chromospermum, T. atroviride, T. versicolor + T. chromospermum and T. versicolor + T. atroviride, respectively. To decrease the cost of sterilization, corn straw was pretreated by T. versicolor + T. atroviride and T. versicolor + T. atroviride with 1∶9, 1∶4 and 1∶1 of the ratio of precolonized carrier and substrate for 30d. During T. versicolor + T. chromospermum and T. versicolor + T. atroviride, pretreatment with an inoculum/substrate ratio of 1∶9, 1∶4 and 1∶1, the degradation rate of lignin were 30% ~ 40%. Therefore, precolonized carrier inoculum is an effective pretreatment method to decrease cost due to precolonized carrier can adjust the unsterilized condition and degrade lignin effectively. 