High-throughput 16S rRNA gene sequencing technology was used to analyze the diversity, structure and function of sediment bacterial communities in four treatment groups (control, oxidizd sediment amendment, probiotics and combined application of two amendments). Combined with the changes of physicochemical properties of sediment, the mechanism of action of different amendments was discussed. The results revealed that sediment total nitrogen, total phosphorus, and organic matter content changed significantly over time, and the amendment treatments tended to increase these nutrient levels in the later culture stage. The combined application group significantly increased the diversity of bacterial community, enhanced the functions of amino acid metabolism, transport and catabolism, promoting nutrient cycling and organic matter degradation. Especially in June, the combined application group showed a synergistic enhancement effect of bacterial community and function. This study revealed the comprehensive regulation and mechanism of the two amendments alone and in combination on the sediment of crab culture, and provided important support for the healthy culture of Chinese crab.