The high temperature annealed CrCoNi medium entropy alloy (MEA) was processed by asymmetric rolling (AR) at room temperature and asymmetric cryorolling (ACR) with rolling speed ratios of 1.0, 1.2, 1.4 and 1.6, then the rolled sheets were annealed at 873, 973 and 1073 K for 0.5 h. The microstructure of the rolled samples was characterized by transmission electron microscope (TEM). It is found that the grain size of the rolled samples decreases with the increase of speed ratio and there are obvious twins. AR experiments at room temperature show that the tensile strength of both the rolled and annealed alloys increases with the increase of rolling speed ratio. The strength of material prepared by ACR is higher than that of rolling at room temperature, but the influence of the speed ratio during ACR on the strength of material is not obvious. In the process of ACR, due to the accumulation of internal stress and rolling defects, the reinforcement of speed ratio has a certain degree of saturation. The fracture morphology of tensile specimens was characterized by field emission scanning electron microscope (FE-SEM). It is found that the alloy has obvious deep dimples after AR, while dimples by ACR is shallow, which is shear fracture.