Abstract: The S355ML steel used in extremely cold areas has the characteristics of high strength and strict requirements for low-temperature toughness. By reasonably selecting welding materials and controlling the preheating temperature, maximum interlayer temperature and heat input, a submerged arc welding process for S355ML in extremely cold areas with a low-temperature toughness requirement of -50 degrees Celsius has been developed. The results of the welding process qualification test of submerged arc welding show that the strength of the joint meets the requirements, the plasticity is good, and the low-temperature toughness far exceeds the qualified value of the project. The process development is successful.