The invention relates to a semiautomatic argon tungsten-arc welding technological process of a bimetal compounding sea pipe, a labour hand-held semi-automatic welding gun welding is adopted, a wire feeder continuously feeds wires, and argon gas is utilized as protective gas. The technological process comprises the following operation steps of: firstly, procedure preparation before welding: manufacturing a groove, picking up fitting the groove, and selecting a welding material; secondly, backing welding process: adopting single layer one-pass welding, wherein two welders respectively stand thetwo sides of a welding seam so as to finish the backing welding; thirdly, hot-runner welding procedure: adopting single layer two-way welding and two-person welding; fourthly, filling welding procedure: adopting five-layer two-way welding and the two-person welding, and dismantling the protective gas after welding four layers; and fifthly, a cover surface welding process: adopting the single layer one-pass welding. The technological process provided by the invention has the advantages of high welding quality, small labour intensity, low construction cost, and high production efficiency; and the technological process is suitable for a compounding submarine pipeline and welding procedure of a subsidiary vertical pipe of the compounding submarine pipeline, and is suitable for the welding of a deep water composite material pressure container and deep water pipe manifold nickel base alloy and the like.