Abstract: The paper studies the properties of Q345R pressure vessels steel plates produced by conventional and TMCP hot continuous rolling processes respectively.The effect of Nb-Ti microalloyed on properties and relationship between microstructure and properties are investigated.The results show that the impact energy of Nb-Ti microalloyed plates is 2 ~ 3 times of that made by conventional process,at the same time,the impact toughness of weldments is higher than that of the plate made by conventional process and the degree of hardening in coarsen zone of hot continuous rolling weldments is less.The better properties of continuous rolling plates come from refined microstructure of base and weldments as low carbon Nb-Ti microalloyed design plus TMCP technology.