To determine the taxonomic position of mineral-weathering bacterium L11 isolated from soil of potassium mine tailing of Nanjing and to elucidate the weathering mechanism of the strain, which will offer the basis for the interaction between microorganism and mineral.16S rRNA gene was sequenced and neighbor-joining phylogenetic tree was constructed to identify strain L11. The ability of strain L11 to weather potash feldspar was evaluated by shaking culture. Scanning electron microscope and Energy-dispersive spectrometry were used to observe the mineral weathering and to analyze the elements of mineral surface, respectively. Mineral (< 2 microm in diameter) was determined by X-ray diffraction.Phylogenetic analysis of strain L11 based on 16S rRNA gene sequence was closest to Bacillus altitudinis (99.9%). Mineral dissolution experiments showed that strain L11 dissolved potash feldspar and significantly released more Si, Al and Fe elements by producing more organic acids. Many bacteria and some spherical minerals were observed on the surfaces of the feldspar and the energy-dispersive spectrometry analysis showed that the new minerals contained more Fe. After 30 days, siderite might be the newly-formed mineral identified by X-ray diffraction in the mineral weathering process.Strain Bacillus sp. L11 could accelerate weathering of potash feldspar, change mineral surface morphology and induce the formation of new mineral complex.