Phosphorus-solubilizing bacteria drive soil organic phosphorus mineralization (phoD gene) and inorganic phosphorus dissolution (pqqC gene) by secreting organic acids or phosphatases, and are key biological factors for enhancing the availability of phosphorus in coastal tidal flat saline soil. To explore the effect of biochar combined with salt-tolerant trees on the phosphorus cycling bacterial community in coastal tidal flat saline soil, this study takes the Dafeng Forest Farm in Yancheng, Jiangsu Province as the research object. Eight salt-tolerant tree treatment groups were set up, namely the group without biochar application and no tree growth (CK), the group with biochar application alone (BC), and the group with biochar application and separate planting of neem (KL), Sapium sebiferum (WJ), pecan (SHT), elm (YS), zelkova (JS), Xanthoceras sorbiferum (WGG), Metasequoia glyptostroboides (ZSS), and acacia (CH). A total of 10 treatment groups were used for field experiments. The absolute abundances of pqqC (inorganic phosphorus dissolution gene) and phoD (organic phosphorus mineralization gene) were determined by fluorescence quantitative PCR (qPCR), and the characteristics of bacterial communities containing pqqC and phoD genes were analyzed by combining Illumina MiSeq high-throughput sequencing technology. The results show that the application of biochar alone and the combination of biochar and salt-tolerant trees are more effective in regulating the phosphorus cycling bacterial community in coastal tidal flat saline soil compared with CK. Especially the treatment of biochar combined with salt-tolerant trees, the pH of the saline soil decreased by 0.26-1.89, and the EC decreased from 2.01dS/m to 0.7-1.97dS/m. Moreover, it increased the contents of SOM, TP, AP, TN, TK in the saline soil, the activities of alkaline phosphatase and phytase, as well as the abundance of pqqC and phoD functional genes (with a maximum increase of 5%), among which the combination of biochar and pecan (SHT) had the best enhancement effect. The combination of biochar and salt-tolerant trees significantly increased the number of OTUs in the phosphorus cycling bacterial community of saline soil, enriching the dominant phosphorus cycling bacterial communities such as Pseudomonas and Bradyrhizobium. The results of redundancy analysis (RDA) indicated that the distribution of phosphorus cycling flora was significantly associated with soil organic matter (SOM), available phosphorus (AP), and enzyme activity (ALP, PHY) (P<0.05). The random forest model concludes that AP is the key environmental factor driving the bacterial community containing pqqC and phoD genes in the coastal tidal flat saline soil. In conclusion, the treatment of biochar combined with salt-tolerant trees can enhance the diversity and richness of the phosphorus cycling bacterial community structure through the "biochar - plant - microorganism" ternary interaction, significantly improving the bioavailability of phosphorus in coastal tidal flat saline soil. Among them, the treatment of biochar combined with pecan (SHT) has the best regulatory effect on the phosphorus cycling bacterial community in coastal tidal flat saline soil. The results can provide theoretical basis and practical reference for carbon sequestration in optimizing the bacterial community structure of phosphorus cycling in coastal tidal flat saline soil and enhancing its phosphorus availability.