The low cycle strain fatigue of steel 16NiCo was investigated in details, and the cyclic stress-strain behaviors were discussed and analysized. The results have shown that the strain fatigue strength of steel 16NiCo is comparable to the same kind of steel AF1410 produced in U.S.A., and the cyclic softening would occur during the cycle loading. In addition, the analysis and calculation for plastic strain energy have indicated that the best combination of the strength with ductility of steel 16NiCo can be achieved under standard heat treatment.