Dielectric ceramic high in energy density in low electric fields and a preparing method thereof are disclosed. The chemical formula of the dielectric ceramic is (1-x)BaTi<3>-xBaSnO3, wherein the x is a mole ratio, and 0.03<=x<=0.15. The dielectric ceramic having high energy storage performance in low electric fields is prepared by the preparing method adopting solid synthesis. According to the dielectric ceramic and the method, components and process steps are simple, operation is easy and repeatability is good. The dielectric ceramic is mainly used for the fields of portable and wearable electronic devices having a high integrated level and a small size.