Changes in the UV-visible and fluorescence characteristics of DOM from the co-composting process of municipal sludge with two types of biochars were discussed. The results showed the aromaticity and humification of DOM from the co-composting with biochars significantly increased compared with control, which indicated in favor of improving the maturity of compost. The treatment with biochar from peanut shell showed the highest maturity, followed by wheat straw biochar. After 21days, compost treated with biochar from peanut shell reached its maximum maturity, while that treated with biochar from wheat straw continued to increase over the whole time. Meanwhile, the DOM from the compost with or without treatment was found to be autochthonous, FI>0.7, BIX>0.8, mainly attributed to the microbial decomposition of compost. Thus, the spectral characteristics of DOM are capable of assessing the degree of maturity of compost during the co-composting process with biochars from different source.