Abstract: The laser butt welding of 10 mm thick X65 pipeline steel plate under the laser power of 10 kW, welding speed of 20 mm/s and defocusing amount of+10 mm was carried out, and the microstructure, mechanical properties and corrosion resistance of the welded joint were studied.The microstructure of the matrix, weld zone and heat affected zone of the sample were observed.The hardness test of the specimen was carried out by hardness tester.The electrochemical corrosion test of the weld and base metal was also carried out. The results show that the section of the welded joint presents the macroscopic morphology of "glass shape", and the weld forming is continuous and full without obvious defects. The microstructure of the weld zone is mainly lath martensite, and the weld zone has the highest hardness value, followed by the heat affected zone, and the matrix has the lowest hardness value.The corrosion resistance of the weld is worse than that of the base metal.Due to high dislocation density of martensite in the weld zone, the weld zone is more prone to corrosion.