Using the parabolic potential as confinement potential in quantum dot and using a finite difference method to discrete the Schrodinger-Poisson equations, an numerical self-consistent solution of three-dimension cube GaAs quantum dot is carried out based on spin-density-functional theory (SDFT). The electronic properties such as total ground state electronic energy, electron density are obtained, and a comparison with the electron density of the two-dimension square GaAs QD with same condition (electron number, spin, length) is hold.