Abstract: The paper studies the effect of heat input energy on the weld metal structure and performance of 06CuNiCrMoNb steel.The results show that there are important influences of heat input energy on weld metal structure and properties.For the structure of the welds, the acicular ferrite decreases, granular bainite increases, and the pro-eutectoid ferrite becomes coarse with increase of heat input energy.The low-temperature impact absorbed energy of the weld metal decreases with increase of heat input energy.