Abstract: The isothermal compression deformation behavior of a modified cobalt alloy was investigated at temperatures from 850 to 1 150 12 with Gleeble-1500 simulation machine. The experimental results show that the alloy has excellent high-temperature mechanical properties. Its maximum flow stress at 850 12 is in the range of 360-475 MPa when the strain rate is between 0. 0021 and 2.1 s^-1. The flow stress of the alloy during high temperature deformation can be described by Zener-Hollomon parameter.