We have investigated the electronic structures and chemical bonding of four tungsten borides, including two WB2 compounds with different crystal structures, α-W2B5 and ε-WB2.5, by ab initio calculations based on density function theory (DFT). The calculated density of state (DOS) shows that all compounds are metallic. The DOS at Fermi level is mainly contributed from 5d states of W atoms. The strong covalent bonds of boron atoms make these compounds stable. Due to a lack of electrons in boron sublattices, weak ionic bonds are generated. The charge density distributions indicate the solid B layers or B polyhedrons are interleaved by the W layers.