Abstract: Objective In order to analyse the differences in microstructure and mechanical properties of segmented welds in the full position welding process of large diameter to thickness ratio stainless steel conduits. Methods The pulsed TIG full-position welding test was carried out on the stainless steel pipe with an outer diameter of 52 mm and a thickness of 0.8 mm. The control method of setting the process parameters in the segmented section was used to optimize the weld forming. The macro morphology, microstructure and tensile properties of the weld were studied by section method. The influence of different melted pool forces on the macroscopic forming and mechanical properties of the weld during the full- position welding process was evaluated. Results The results showed that setting parameters of the segments during full-position welding process could be effectively applied to the pipe girth weld with a large diameter to thickness ratio. The inner and outer surfaces of the weld behaved good gloss, there was no need to polish. The surface depression in the inside and outside of the weld was less than 0.1 mm. The uniformity of segmented weld width was good, and the ratio of the upper welding width to the bottom was around 1.1. The microstructure of the weld center was composed of fine columnar austenite dendrites and interdendrite ferrite, with a narrow heat-affected zone and a narrow band of fine grains between the semi-melted region and the columnar crystals. The tensile strength of each section had little difference, the average value reached 534 MPa, up to the requirements of first-class welding standard. Conclusion Setting the process parameters in the segmented section of full position welding on thin-walled stainless steel pipes, the appearance and internal quality could up to the requirements of first-class welding standard, which could met the production requirements of pressurized conveying system pipes in the aerospace industry.