Abstract: Due to the inhomogeneity of offshore platform structure and the limitation of welding technology,the welded joints were prone to appear cold cracks. For the problem,based on SYSWELD,the weld of typical Y-joints of offshore platform jacket made of E36 high strength steel was modeled and the welding process was numerically simulated in the paper. According to the stress field,the restraint stress was obtained,so as to realize the quantitative evaluation of its cold cracking. The heat source model was applied through the thermal cycle obtained by the heat source check,and then the changes of axial,circumferential and radial restraint stresses along the intersection line at the weld root and the weld toe were analyzed and the restraint stress of dangerous points in each direction were compared with the critical restraint stress of the material. The results showed that the maximum restraint stress was 492 MPa,which was less than the critical restraint stress of E36 high strength steel. That was to say,there would be no delayed cracking at the root and toe of Y-joints.