[Objective] The paper was to study the bioactive characteristics of soil microorganisms in different-aged orange plantations. [Method] Taking 010 cm deep soil in 3 orange plantations with different planting years in suburb of Yichang City as the test object, the variation rule of total organic carbon, total nitrogen, soil pH value, microbial biomass carbon, microbial biomass nitrogen, number of 3 main types of soil microbial flora, basal respiration, microbial entropy and metabolic entropy in differentaged orange plantations was studied. [Result] With the increase of planting years, the soil acidification of different-aged orange plantations was aggravating; total organic carbon and total nitrogen content increased first and then decreased; the total number of soil microorganism showed a downtrend, of which the number of bacteria decreased significantly, the number of actinomycetes had small changes, the number of fungi increased significantly, and the ratio of bacteria and fungi in soil （B/F） showed a decreasing trend. Soil microbial biomass carbon was fluctuated within a small range, whereas soil microbial biomass nitrogen decreased significantly; soil microbial entropy decreased significantly, and metabolic entropy showed an increasing trend. This indicated that the decrease of soil pH value affected the changes of soil microbial flora, microbial activity, microbial biomass carbon and nitrogen and soil major nutrients, and further affected the normal exertion of soil function. [Conclusion] The study explores soil nutrient characteristics and changes of microbial flora in test area, which will provide scientific basis for further study on orchard soil and orchard management.
