Abstract: BackgroundLong-term intensive cultivation in the black soil region of Northeast China has caused soil nutrient imbalance and microbial functional decline,constraining agricultural sustainability.This study aimed to systematically evaluate the effects of maize-legume cover crop rotation on soil microbial entropy and soil-microbe stoichiometric imbalance, and to reveal their interrelationship, thereby providing a basis for nutrient management and soil quality improvment. MethodsFive legume cover crop treatments including alfalfa, hairy vetch, white clover, alfalfa-hairy vetch mixture, and alfalfa-white clover mixture were compared with maize monoculture (CK). SOC, soil total nitrogen (TN), soil total phosphorus (TP), soil microbial biomass C/N/P, stoichiometric ratios, microbial entropy (qMBC, qMBN, qMBP), and stoichiometric imbalance indices (C:N_imb, C:P_imb, N:P_imb) were measured. Redundancy analysis (RDA) was employed to identify the dominant drivers. Results1) Cover crop treatments significantly increased soil SOC, TN, TP contents and microbial biomass C, N, P levels, and markedly enhanced microbial entropy, with the qMBC under alfalfa (+116.1%) and the qMBP under alfalfa-white clover mixture (+92.5%) being most pronounced. 2) Overall, leguminous cover crops decreased soil C:P, N:P, and C:N_imb, thereby alleviating soil-microbe stoichiometric imbalance. However, the alfalfa-white clover mixture, despite markedly enhancing microbial entropy, exhibited higher C:P_imband N:P_imb, suggesting a potential risk of aggravated P limitation under low-P conditions. 3) Microbial biomass C, N, and P were identified as the key factors regulating microbial entropy and stoichiometric imbalance, and a tight coupling relationship was observed between the two.ConclusionsOverall，Leguminous cover crops improve soil nutrient supply and C-N-P stoichiometry, there by enhancing microbial entropy and alleviating C:N imbalance. Alfalfa monoculture and alfalfa-white clover mixture showed the strongest regulatory effects, though mixture systems should be optimized with respect to soil P status to avoid aggravating C:P and N:P imbalance. These findings provide mechanistic insights into how leguminous cover crops restore black soil functions and support nutrient management under conservation agriculture.