Thermomechanical processes combined with reverse transformation from (ε-hcp and M2N) dual-phase to γ-fcc phase of biomedical Co-Cr-Mo-N alloys were examined. According to XRD analysis, the reverse transformation from ε + M2N to γ is completed after heat treating at 1223 to 1373 K without deformation, while after heat treating at 1223 and 1273 K contained residual M2N particles in the γ matrix. After the subsequent hot compression at condition at 1273 K and strain rate less than 1 s-1, and 1223 K and strain rate less than 10 s -1, ultra fine grains less than 1 μm with residual M2NN were obtained. Therefore, it is suggested that the residual M2NN suppressed further growing of DRXed grain. The obtained microstructure with ultra fine grain dispersed with residual M2NN was obtained to demonstrate both grain refining strengthening and precipitation strengthening.