Abstract: The most commonly used pressure vessel steel Q345R in China was investigated by means of the impact test and fracture toughness test. The widely used empirical correlations of fracture toughness in the international standards were collected. Combining with the experimental data of material properties, the accuracy of these correlations used to estimate the fracture toughness in the transition temperature range of Q345R steel was analyzed. The results show that the Sailors-Corten and Wallin empirical correlations have good agreement with the measured fracture toughness and can be used to estimate the fracture toughness of Q345R steel during the transition temperature range. Furthermore, the specific correlation between impact energy and fracture toughness for Q345R steel was established based on the measured data of material properties.