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This study aims to screen strains with the ability of both degrading straw and promoting crop growth from Shajiang black soil for solving problems such as difficult survival status, weak rot-promoting effect and poor crop growth caused by exogenous rot straw. Screening with sodium carboxymethyl cellulose plate and combing with CMC enzyme (endo-1, 4-β-D-glucanase)-and IAA (Indole-3-acetic acid)-producing capacity, the potential straw rot-and plant growth-promoting were evaluated. Species identification of strains were conducted via morphological, physiological and biochemical and 16S rDNA sequence analysis, then straw degradation shake flask and corn pot test were used to determine the actual rot-and growth-promoting effect of the strain, and a single factor test was set up to explore the optimal condition for growth and enzyme production of the strain. The screened strain n3 demonstrated the high activity of CMC enzyme (20.60 U/mL) and IAA synthesis (20.15 mg/L), and was identified as Azospirillum zeae. The results showed that inoculation with n3 increased the rate of straw rot-promoting under liquid fermentation by 54.71%(P< 0.01) compared with the control treatment; the root length, average diameter and SPAD value (Soil and plant analyzer development) of maize under soil culture conditions increased by 18.3%, 22.0% and 5.24%, respectively (P< 0.05). The optimal nitrogen source and liquid volume of n3 growth, yielding CMC enzyme and IAA were the same as that of yeast powder and 25 mL/250mL, but the optimal pH was 5.0 for CMC enzyme production, and 6.0 for growth and IAA production. Conclusively, the screened A …