Nano-catalytic materials have broad application prospects in solving bacterial resistance caused by overuse of antibiotics. However, their catalytic efficiency usually depends on a lower pH value range (i.e., pH=2.0-5.0) rather than on a weakly acidic bacterial microenvironment (i.e., pH=6.0-7.0), leading to an limited catalytic efficiency and an insignificant bactericidal effect. In this paper, MnSiO3 samples were prepared by a simple co-precipitation method. The morphology, structure and catalytic properties of the samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and ultraviolet-visible spectroscopy (UV-Vis). The antibacterial performance against E. coli and S. aureus were investigated. The results show that the morphology of amorphous MnSiO3 samples transforms from nano-sized particles to micron-sized blobs in buffer solutions at pH 6.4 and 7.0. MnSiO3 nano-sized particles had an intense catalytic ability at a higher pH value and an excellent antibacterial performance against E. coli and S. aureus. Therefore, the in-situ structure transformation of MnSiO3 presents a promising treatment strategy for bacterial infection.