An effective interatomic potential is crucial for molecular dynamics simulations. A more effective potential is proposed. One of the characteristics of this potential is the introduction of the parameter reff to calculate the electrostatic interactions among atoms. The pair-correlation functions and X-ray diffraction patterns of cubic and tetragonal Barium Titanium are derived from molecular-dynamics simulations with the use of the new potential function. Lattice constants and elastic constants are also calculated. The calculated results agree well with the experimental data, which suggests that this potential is promising in describing the thermodynamic or mechanic properties of Barium Titanium.