Soil respiration (Rs), driven by microbial activity, varied with mulching practices, but the microbial mechanisms behind these differences remain unclear. To address this knowledge gap, a three-year (2019–2021) maize field study was conducted to evaluate three treatments: no mulching (CK), plastic film mulching (PM), and straw mulching (SM). This study assessed the effects of these practices on the alpha diversity and structure of the bacterial community and Rs, and explore the roles of soil abiotic and biotic factors in driving Rs. The results indicated that PM significantly increased bacterial alpha diversity (as indicated by ASVs, Chao1, and Shannon indices) in the early growth stage of maize and decreased the bacterial abundance and alpha diversity in the mid-to-late growth stages, whereas SM significantly increased that. Furthmore, PM and SM significantly altered the bacterial community, with PM increasing oligotrophs (e.g., Chloroflexi and Firmicutes), while SM increasing copiotrophs (e.g., Proteobacteria and Acidobacteriota). Cumulative Rs under PM varied interannually, increasing in 2019 and 2020 but decreasing by 9.1% in 2021. In contrast, SM consistently stimulated cumulative Rs by 31.8–72.4%. Correlation and redundancy analysis identified soil moisture, NH + 4-N and NO–3-N as key factors shaping the bacterial community. Structural equation modeling revealed that bacterial community structure, NH + 4-N, NO–3-N, and soil temperature (ST) exerted greater total effects on Rs, with NH + 4-N indirectly affect Rs via bacterial community structure. Overall, PM suppressed Rs in 2021 maize season mainly by enriching oligotrophs under high ST in the summer, whereas SM promoted Rs via enhancing copiotrophs involved in soil carbon cycling. This study elucidated the contrasting microbial pathways through which different mulching practices modulate Rs in summer maize cropping systems.