We report a self-consistent full-potential linear muffin tin orbitals(LMTO) band structure calculation on the electronic and magnetic properties of Ru-based perovskite SrRuO3(SRO) in this article. For the assumed simple cubic SRO with lattice constant a=0.392nm, the calculated spin moment per SrRuO3 unit is 1.29μB. Most part of this spin moment (approximately 65%) is located on the Ru site within a unit cell. The density of states (DOS) of electrons near the Fermi energy is 43.5 (states/Ryd/f.u.). For real orthorhombic SRO, our LSDA calculation predicts a ferromagnetic ground state with 1.08μB moment per unit formula. The Sommerfeld constant is 10.60mJ/mol·K2 deduced from the calculated DOS near the Fermi energy. All these findings showed that SRO is an itinerant ferromagnet with wide energy bands.