Abstract: Based on the characteristics of diverse types and complementary properties of organic wastes, multi-material co-composting has become a prevailing trend. Organic wastes can not only be uesd as composting raw materials, but can also be converted into biochar through pyrolysis, which can be used as external additives to regulate maturity and humification during composting. Therefore, this study used pig manure, kitchen waste, and corn straw as raw materials for co-composting.At the same time, above three raw materials were transformed into different biochar (pig manure biochar, kitchen waste biochar, and stover biochar) through high-temperature pyrolysis, which were added into the pile to investigate the effects of three biochar from different sources on the maturity and humification during the co-composting.The research results were as follows: three types of biochar promoted the temperature rise during composting and improved the compost maturity. Among them, the maturity of the compost treated with pig manure biochar and stover biochar increased significantly, and the seed germination index (GI) of the compost products was 23.42% and 16.84% higher than that of the control group, respectively. Meanwhile, both stover biochar and kitchen waste biochar could promote the humification of composting. The ratio of humic acid to fulvic acid (HA/FA) of the compost products was 67.31% and 65.38% higher than that of the control group, respectively, while the treatment with pig manure biochar was slightly lower than that of the control treatment. Therefore, the treatment with stover biochar could simultaneously enhance the compost maturity and the degree of humification. The correlation analysis indicated that stover biochar could improve the compost maturity by reducing the electrical conductivity (EC) and the content of ammonium nitrogen (NH₄⁺-N) of the compost, and promote the formation of humus in the compost by regulating nitrogen transformation, thereby enhancing the degree of compost humification. This is related to the large specific surface area and abundant pore structure of stover biochar. In conclusion, adding corn stover biochar in multi-material co-composting can simultaneously enhance the compost maturity and the degree of humification.