Abstract: [Objective]In order to reveal the effect of reducing the amount of novel nano-carbon humic acid water-retaining fertilizer (CSF) on soil microbial communities structure and citrus growth.[Method] In this study, conventional fertilization was as the control (KC1) in Wanzhou citrus orchard of Three Gorges Reservoir area. Reduction of CSF 0%(KC2), 10% (KC3), 20% (KC4), 30% (KC5) and 40% (KC6) were used to analyze the changes of soil bacterial community structure, citrus yield and quality. [Result]The results showed that the Observed-species, Shannon index, Chao1 index and PD_whole_tree of KC6 were higher than those of KC1, and were the same as KC2. The abundance of Kanthocyanidaeae was the highest in KC5. Compared with KC1, the Kanthoxicaceaeaceae in KC3, KC4 and KC6 were significantly decreased, and the levels of Nitrosomonadaceae and Pseudomonasaceae were higher than that of KC1 after the treatment of KC6. Sphingomonas was lower than that of KC1, but Burkholderia and Pseudomonas were significantly higher than those of KC1.. It was found that the similarity among treatments was small after bacterial community similarity clustering analysis, and the yield of citrus was reduced by CSF after fertilization, when the fertilization was reduced by 30%, the yield was increased by 4.50%, whist the CSF was reduced of 40% the yield was reduced of 4.14%. After the application of CSF compound fertilizer, citrus quality in the CSF constant fertilization and reduction of 10% and 40%, the quality did not significantly change, and in the reduction of 20%, 30%, the quality was significantly decreased.[Conclusion]The results showed the diversity of soil bacterial community structure, the yield and quality of citrus were changed with the reduction of CSF fertilization.