High-throughput sequencing technology was used to investigate the effects of different types of Trichoderma fungi and their composite inoculants on yam growth, as well as soil physicochemical properties and microbial communities under field conditions. The results showed that, compared with the control without Trichoderma strain inoculation (CK), treatments with inoculation with Trichoderma guizhouense NJAU4742 (T1), Trichoderma longibrachiatum JS84 (T2), Trichoderma longibrachiatum MD30 (T3), and the composite inoculant of these three Trichoderma strains mentioned above (T4) all increased plant height, leaf length and width, and yield of Chinese yam. Specifically, compared with the control, yam yields under T1, T2, T3, and T4 increased by 7.29%, 26.37%, 1.38%, and 31.77%, respectively. Nevertheless, only T4 exhibited a significantly higher yield. Principal coordinates analysis (PCA) revealed that Trichoderma inoculation significantly altered soil bacterial and fungal community compositions, promoting the growth of beneficial microbial genera such as Bacillus and Trichoderma. Further redundancy analysis (RDA) indicated that soil available potassium content was one of the key nutrient factors driving the assembly of soil bacterial and fungal communities, showing a strong correlation with Bacillus and Trichoderma genera. Mantel's correlation analysis further found significant positive correlations between yam yield with the contents of soil organic matter, available potassium and phosphorus. This study demonstrates through field experiments that the application of Trichoderma inoculation can promote yam growth and yield, with composite microbial inoculants showing the best growth-promoting and soil-amendment effects. The findings provide technical support for utilizing functional microbes to promote Chinese yam growth..