Abstract: The crystal structure, electronic structure, magnetic moment and dielectric function of an element (M=Fe, Mn) doped with cubic BaTiO3 (in which the chemical formulas are BaFexTi1-xO3 or BaMnxTi1-xO3, and x is 0, 1/8, 1/4, 3/8 or 1/2) are calculated by using the first principle method under the framework of the density functional theory. The results show that, when x is 1/8, the crystal structure of BaTiO3 remains cubic phase, while, when x is greater than 1/8, the crystal structure of BaTiO3 changes into tetragonal ferroelectric phase. The addition of Fe or Mn makes BaTiO3 obtain great magnetism, and the total magnetic moment mainly comes from the contribution of the local magnetic moment of Fe or Mn ions. With the increase of element doping, the magnetism of BaTiO3 increases. At the same time, by comparing the static dielectric constant before and after doping, it is found that the doping of element Fe or Mn makes the static dielectric constant of BaTiO3 change greatly, which is much larger than that of the undoped BaTiO3. Therefore, Fe and Mn are easier to obtain the high dielectric constant.