Abstract: An investigation on solubility of WC in cobalt. cobalt modification and its magnetic properties, lattice parameters, mechanical and corrosive properties has been made in the present paper,The results show that the solubility of WC in cobalt phase decreases with the decrease of temperature. The Cobalt phase state can be precisely characterized and the solubility of WC in cobalt phase can also be determined by testing the magnetic properties and the lattice parameters of cobalt. The mechanical and corrosive properties of cobalt phase are affected by the contents of both tungsten and carbides soluted in cobalt. It is of great significance preventet het ransition from α-Co to ε-Co in order to prolong the performance durability of materials.