Soil salinization/alkalization is a complex environmental factor that includes not only neutral salt NaCl but also other components like Na₂CO₃. miRNAs, as small molecules that regulate gene expression post-transcriptionally, are involved in plant responses to abiotic stress. In this study, maize seedling roots were treated for 5 h with 100 mM NaCl, 50 mM Na₂CO₃, and H₂O, respectively. Sequencing analysis of differentially expressed miRNAs under these conditions revealed that the Na₂CO₃ treatment group had the most differentially expressed miRNAs. Cluster analysis indicated their main involvement in the regulation of ion transport, binding, metabolism, and phenylpropanoid and flavonoid biosynthesis pathways. The unique differentially expressed miRNAs in the NaCl treatment group were related to the sulfur metabolism pathway. This indicates a significant difference in the response patterns of maize to different treatment groups. This study provides theoretical evidence and genetic resources for further analysis of the molecular mechanisms behind maize’s salt–alkali tolerance.