Abstract: In order to study the welding joint performance of steel for offshore wind power, this work takes S460steel as the research object, and uses welding thermal simulation method to simulate the coarse grain zone in its welding heat affected zone. Continuous Cooling Transformation Diagram are established, and the microstructure and performance characteristics of the heat affected zone with different line energies in the coarse grain zone are studied. The research results indicate that S460 steel has good adaptability to welding wire energy, welding joints have excellent comprehensive performance, and the heat affected zone has low hardenability, which can meet the technical requirements of high-performance thick plate large wire energy welding for large capacity wind power.