To mitigate the challenges associated with straw returning to the field, this study utilized straw returning soil as the bacterial source and identified four cellulose-degrading strains through enrichment culture and Congo red staining. They were identified by molecular biology as Penicillium vinaceum, Hypocrea sp., Phanerochaetc chrysosporium, and Alternaria. By assessing the activities of filter paper enzyme, carboxymethyl cellulase, and microcrystalline cellulase, the results showed that Penicillium vinaceum exhibited the most effective straw degradation, with enzyme activities of filter paper enzyme, carboxymethyl cellulase, and microcrystalline cellulase enzyme activities were 102.13 IU/mg, 153.45 IU/mg, and 144.22 IU/mg, respectively, significantly surpassing the other three strains. The optimal growth conditions for this strain were 25℃, pH 3.0, and a substrate concentration of 3 g/L. Mechanistic analysis revealed that the high efficiency of Penicillium vinaceum in cellulose degradation was attributed to an enzyme synergy system: the bacterial strain synergistically completes the decomposition of straw through the dissolution of cellobiohydrolase I and Lytic polysaccharide monooxygenases, as well as the separation of cellobiohydrolase II and endoglucanase. This study provides a superior candidate strain for the development of degradation agents to address the obstacles of straw returning to the field.