The invention discloses a welding process for 1,000MPa level non-quenched and tempered high-strength steel. Under the indoor operating environment at the temperature of higher than 5DEG C, and argon and carbon dioxide mixed gas shielded welding is adopted for backing welding, filling and cosmetic welding. The welding process comprises the following steps of: (1) determining welding process parameters; (2) preparing before welding: preparing grooves and performing butted assembly; (3) assembling to meet the requirement of tack welding; (4) performing backing welding by adopting argon and carbon dioxide mixed gas shielded welding; (5) performing filling and cosmetic welding by adopting the argon and carbon dioxide mixed gas shielded welding; and (6) performing integral low-temperature ageing treatment. The welding process solves the problem of welding the 1,000MPa level non-quenched and tempered high-strength steel, a welding joint has good comprehensive mechanical properties and the tensile strength same as a base metal, and welding cracks are avoided.