This　work　investigates　the　proposed　welding　of　stainless　steels　with　no　backing　gas　by　using　solid　wire　ER316L-Si　and　mixed　gases　(He+Ar+CO2).　The　protection　mechanism　was　also　discussed　from　the　view　of　arc　physics　and　the　alloy　elements　in　the　solid　wire.　The　result　shows　that　when　the　proportion　of　helium　in　the　above-noted　mixed　gases　excesses　45　percent,　the　mechanical　properties　and　the　intergranular　corrosion　tendency　meet　corresponding　Chinese　standards.　Further,　the　alloy　elements　in　the　solid　wire　can　react　with　oxygen　during　the　period　of　high　temperature　boosted　by　helium　arc;　this　result　in　the　formation　of　a　bed　of　thin　slag,　which　can　avoid　the　oxidation　of　the　backing　weld　and　eliminate　the　need　of　backing　gas.　©2009　Editorial　Board　of　CHINA　WELDING.