It is well studied that potassium (K⁺) deficiency induced aberrant growth and development of plant and altered the expression of protein-coding genes. However, there are not too many systematic investigations on root development affected by K⁺ deficiency, and there is no report on miRNA expression during K⁺ deficiency in wheat. In this study, we found that K⁺ deficiency significantly affected wheat seedling growth and development, evidenced by reduced plant biomass and small plant size. In wheat cultivar AK-58, up-ground shoots were more sensitive to K⁺ deficiency than roots. K⁺ deficiency did not significantly affect root vitality but affected root development, including root branching, root area, and root size. K⁺ deficiency delayed seminal root emergence but enhanced seminal root elongation, total root length, and correspondingly total root surface area. K⁺ deficiency also affected root and leaf respiration at the early exposure stage, but these effects were not observed at the later stage. One potential mechanism causing K⁺ deficiency impacts is microRNAs (miRNAs), one important class of small regulatory RNAs. K⁺ deficiency induced the aberrant expression of miRNAs and their targets, which further affected plant growth, development, and response to abiotic stresses, including K⁺ deficiency. Thereby, this positive root adaption to K⁺ deficiency is likely associated with the miRNA-involved regulation of root development.