<p>The effects of weathered coal on the maturity of sheep manure compost were investigated by studying the spectral changes in dissolved organic matter (DOM) in sheep manure compost. Sheep manure was used as the raw material for compost fermentation, with 10% and 15% weathered coal added. Total organic carbon analysis, ultraviolet–visible absorption spectroscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy, and three-dimensional excitation emission matrix fluorescence spectroscopy were used to study the spectral changes in DOM in sheep manure compost after the addition of different proportions of weathered coal. Weathered coal had a significant effect on DOM during sheep manure composting. The non-humic organic matter with the same DOM concentration continued to condense to produce humus, increasing the benzene ring structure of the organic matter and enhancing the humification degree of the compost, indicating that the degree of compost maturation increased. Additionally, a portion of humic acid was converted to fulvic acid during composting, and the addition of 15% weathered coal accelerated the composting process. The addition of weathered coal facilitated the synthesis of humic acid in DOM and reduced the soluble salt content in sheep manure. The findings provide a theoretical basis for the collaborative and comprehensive utilization of aquaculture waste and weathered coal resources.</p> Graphical abstract <p></p>