Abstract: The welding technology test is conducted by using activating flux of A-TIG welding for mild steels.Evaluation includes appearance of weld,effect of flux on penetration,microstructure of weld,chemical compositions of weld and base material and mechanical properties.The results indicate that the penetration has been increased 3 times compared with the conventional TIG welding and for the plates of 12 mm thick the full penetration can be get in a single pass without groove preparation.The appearance of weld is fine,there is no effect on the microstructure,the chemical compositions and mechanical properties.Welding current,travel speed,arc length,coating quantity and type of shidlding gas have effect on penetration.