Abstract: 【Objective】 The aim of this study was to screen high-efficiency nitrogen-fixing microbes from high-temperature aerobic compost,and to use the selected high-quality strains to improve the nitrogen content of compost,and to develop bioorganic fertilizers.【Method】 Nitrogen fixing microbial strains were isolated using Ashby nitrogen-free medium from samples collected at the high temperature stage and the mature stage of aerobic high-temperature composting,and the nitrogen fixing ability,optimal growth conditions and growth curves of the microbes were determined. The strains were identified by morphological and physiological characterization,biochemical reactions and 16S rRNA gene sequencing,and the strains were then inoculated back into the compost mixture to study their effects【Result】 The results showed that the nitrogen-fixing ability of the two isolated strains, A3 and B2,was 7. 88 mg/L and 22. 96 mg/L, respectively. A3 and B2 were identified as Nocardiopsis dassonvillei and Bacillus cereus, respectively. Both strains were eutrophic and thermophilic bacteria that could adapt to a wide range of pH and grow rapidly.Both strains were able to produce IAA and siderophore. In addition,B2 could utilize phosphorus,and tolerate salt concentrations of up to 8%. Only A3 was shown to significantly increase the nitrogen content of the compost product,by 28. 5%,while B2 did not have the same effect.【Conclusions】 A3（Nocardiopsis dassonvillei） can be used to improve the nitrogen content of compost,and has the potential to produce nitrogenfixing bacteria bioorganic fertilizers. Given the good nitrogen-fixing ability and other functions of B2（Bacillus cereus）,it has the potential to develop microbial agents.