Using density functional calculations within the generalized gradient approximation and Hubbard U framework, the electronic and the magnetic properties of SrCoO3 are investigated. The result shows that the spin-up t2g and eg states of Co shift toward the lower energy with the increase of the U value, whereas the spin-down t2g and eg states of Co shift toward the higher energy. The O 2p state almost does not shift with the increase of U value. The electronic structure of SrCoO3 changes from metal state into half-metal state around U of 7-8 eV. The magnetic moment of Co ions increases linearly with U increasing for U 7.0 eV, and almost does not change for U 8.0 eV. Compared with the experimental results, U = 8.0 eV is thought to be suited for the study of SrCoO3. The result shows that with U = 8.0 eV, the magnetic moment on Co site is 3.19 B and SrCoO3 has the half-metallic nature.