Abstract: Secure reactor structure plays the role of containing radioactive substances and protecting system from the interference of reactor, which is related to the safe operation of the power, so it is an important structure. Nuclear reactor cylinder prestressed concrete structure with pure rolling steel rebar directly influences the tenacity of secure life. Vanadium microalloyed super strength finish rolled rebar based on air-cooled Mn series bainitic steels was developed in order to meet the needs. Yield strength of vanadium-alloyed air-cooled tempering steel reaches 1 494 MPa, and tensile strength is 1 688 MPa. Effect of vanadium on the strength and snugness, structure and phase transformation was studied by means of SEM and TEM. Besides, morphology, size and distribution of vanadium precipitates were studied.