The medium entropy alloy of CrCoNi has excellent low temperature properties, but its plasticity is poor (<8%) after liquid nitrogen temperature rolling. In this research, arc melting of casted CrCoNi entropy alloy as the research sample, rolling deformation of CrCoNi alloy at low temperature (77K) for three passes, the total deformation was 50%. Then, annealing was carried out at 650 ℃, 700 ℃ and 800 ℃ for 30 minutes. Experimental data show that: CrCoNi medium entropy alloy after rolling and annealing, not material phase structure changed, after annealing. Because of recrystallization, deformation grains become smaller, and generated ∑3 annealing twin in organization. As the annealing temperature increased, the number of recrystallized grains increased, the elongation increased. It can be concluded that through the cold rolling and medium temperature annealing in short time performance controlling, matching the performance of the strength and toughness can be obtained, The efficiency of heat treatment process was improved.