In this study, the collected mangrove sediments were sifted into different groups according to particle size. DNA was extracted from the samples of each group, and 16SrRNA sequencing was performed to obtain the OTU detection results, and community composition was analyzed. After annotation, the microflora at phylum and genus level were mainly observed to observe their distribution composition and changes in different particle sizes. Network analysis was performed to analyze the effects of particle size on species and to show patterns of co-occurrence between species. The diversity results were analyzed to see if there were diversity differences between the Alpha diversity observation groups, and the Beta diversity observation whether different groups were significantly separated. LEfSe analysis observed species with significant differences between groups, combined with element cycling species and genes, to characterize the influence of particle size on the element cycling process. The extracted DNA was sequenced by metagenomic sequencing to study the population structure of microorganisms in different particle sizes, functional activity of genes with functional element cycling, and the relationship between microorganisms and the environment.