Mixed-sowing ornamental plants are colorful, environmentally friendly, and low-carbon, making them widely used internationally. Most research on these plants focuses on aboveground aspects, with minimal attention given to their effects on soil microorganisms. Therefore, this study aims to explore the influence mechanism of various types of mixed-sowing ornamental plants on soil microorganisms. This study measured soil chemical properties, plant richness, and landscape features. High-throughput sequencing was used to analyze soil bacterial 16S rRNA and fungal ITS amplicons, assessing microbial diversity and its correlation with environmental factors. Zero-model was used to evaluate the assembly mechanism of soil microbial community and random matrix theory was used to construct soil bacteria-fungi interdomain ecological network. The results showed that in B and C, dominant and flowering species varied with seasonal dynamics, enhancing the landscape effect of the community. Mixed-sowing ornamental plants had significantly increased ammonium nitrogen (AN) content, and soil bacterial and fungal α diversity. Compared to soil chemical properties, plant richness and landscape characteristics of mixed-sowing ornamental plants had a greater influence on soil microbial communities. All combinations primarily shaped by stochastic processes, but B exhibited a higher degree of stochastic processes. The stability of the interdomain ecological networks at B and C was similar, with B exhibiting slightly better resistance to disturbance than C. In conclusion, B had a moderate number of species, followed by C, with A, having the fewest. This study provides valuable insights for constructing mixed-sowing ornamental plants that promote striking above ground landscapes and heathy subsurface soil.