Abstract: The laser surface hardening for mould-cutting roller of 50 carbon steel is carried out using continuous wave CO2 laser beam.The microstructure observation and hardness distribution testing in the cross-section of the hardened layer are performed.The results indicate that the microstructure of the hardened layer of mould-cutting roller quenched consists of the fine dislocated lath martensite and a small quantity of residual austenite.After laser surface hardening,the mould-cutting roller possesses of small contraction distortion,high hardness,and uniform distribution of hardness.And hence using laser surface hardening process to modify the surface of mould-cutting roller of 50 carbon steel is practicable.