Abstract: [Objective] The Xialei–Longbang area in southwestern Guangxi hosts a critical manganese ore concentration district in China. Current exploration is hindered by an incomplete understanding of the occurrence patterns of sedimentary manganese deposits and a lack of a sound basis for selecting effective exploration methods.[Methods] Based on an analysis of the metallogenic geological settings, this study compares the geological characteristics of typical deposits and the geochemical characteristics of manganese-bearing rock series, and evaluates the results of exploration tests using the multi-polarization magnetotelluric (MPMT) method in the ore concentration district. [Results] The study area can be divided into two secondary manganese-forming basins, namely the Xialei–Shangying Basin and the Longbang–Dizhou Basin. Three sedimentary microfacies types are identified in the Xialei–Shangying manganese-forming basin: calcareous siliceous rock, calcareous siliceous rock–siliceous limestone, and siliceous limestone–argillaceous banded limestone. Only the siliceous limestone–argillaceous banded limestone microfacies occurs in the Longbang–Dizhou manganese-forming basin. Among these microfacies, the calcareous siliceous rock microfacies is the most favorable for mineralization, followed by the calcareous siliceous rock–siliceous limestone microfacies, whereas the siliceous limestone–argillaceous banded limestone microfacies is the least favorable. Centers of manganese enrichment are distributed within a zone approximately 500–1000 m northwest of the Xialei–Lingma synsedimentary fault. The thickness and Mn grades of rhodochrosite ore beds vary considerably among different mining areas (segments). Outward from the Xialei Mining Area, the manganese ore beds gradually thin and their Mn grades decrease. Moreover, the thickness and Mn grade of ore beds II+III generally show positive correlations with those of ore bed I. The ore-forming fluids were dominated by submarine hydrothermal fluids, and the sedimentary metallogenic environment was weakly oxidizing to oxidizing. Compared with the overlying and underlying wall rocks, the manganese-bearing rock series are characterized by a combination of low resistivity and high magnetic susceptibility. [Conclusions] Based on these results, a comprehensive prospecting model for Devonian rhodochrosite deposits was established and validated through exploration tests in the Xialei–Longbang area. The model captures the key ore-controlling factors and prospecting criteria of sedimentary manganese deposits in the region. [Significance] The combination of MPMT and drilling is applicable to sedimentary manganese exploration in southwestern Guangxi and provides important guidance for deep and concealed ore prospecting.