The effects of different content of Nb and V on microstructure and mechanical properties of 23CrNi3MoA Steel were studied. The results show that Nb and V elements played an ultra-refined role in 23CrNi3MoA steel. When the content of Nb and V in microalloy is too high, there exists carbide segregation phenomenon, Nb segregation effect is better than V. When 0.059%V is added, the carbide is evenly dispersed and the steel has good strength, plasticity and toughness.