The isothermal compression deformation behavior of a modified cobalt alloy was investigated at temperatures from 850 to 1150℃ with Gleeble-1500 simulation machine. The experimental results show that the alloy has excellent high-temperature mechanical properties. Its maximum flow stress at 850℃ is in the range of 360~475MPa when the strain rate is between 0.0021 and 2.1s~ -1 . The flow stress of the alloy during high temperature deformation can be described by Zener-Hollomon parameter.