Abstract: HG70 steel is a high strength and low carbon steel for mechanical engineering use. In this paper, the influence of pre-heating temperature on the content of diffusive hydrogen in weld joint was studied. The hardness test in heat-affected zone and Y-groove cracking test are carried out to evaluate cracking sensitivity of this steel. The mechanical properties of welded joint are also examined. The results show that HG70 has low sensitivity to cracking and the welded joint of HG70 steel exhibits good mechanical properties.