Welding is one of the key technologies in pipeline construction. The corresponding welding technology should be meeting the requirements of the pipeline construction due to the rapid development of advanced pipeline steel. The advantages and disadvantages of laser welding for pipeline steel are analyzed. X52 pipeline steels with a thickness of 16 mm are welded using high power CO₂ laser. Cracks in the weld are not detected by X-ray. Solidification properties and microstructure of laser welded joint have been studied by optical microscope. The mechanical tests of the welded joint have been conducted according to American Petroleum Institute Specification API SPEC 5 L.The results show that the ultimate tensile strength is 480 MPa ,fracturing in parent metal,without any cracks in 180°bend specimens;and Charpy notch toughness at -20 ℃ is CVN＝279 J in weld metal,CVN＝282 J in fusion zone and CVN＝212 J in heat affected zone. The maximum hardness of butt welded joint is about 270 HV,which locates in the bottom of weld. All the mechanical properties of weld produced by using laser welding can meet the welding technical requirements of X52 pipeline steel.