The present work has been focused on the effects of surface-active element sulfur on welding properties during 10kW high power laser welding of 304 stainless steel thick plate. Molten pool behavior, morphology feature of sulfide inclusions, metallographic structures, XRD patterns, microhardness, potentiodynamic polarization curves and pitted surface have been investigated and discussed. The results indicated that the added sulfur powder improved the weld depth by increasing molten metal fluidity, elongating molten pool and promoting heat transmission. The observed sulfide inclusions had small particle size of 0.65 mu n in average and were distributed sparsely in weld joint. The WWS (weld joint with sulfur powder) had higher delta-ferrite content and finer grain size than the WWOS (weld joint without sulfur powder) and BM (base metal) due to the effects of sulfide inclusions on crystallizing process. The preferred orientations of gamma-austenite along the (200) and (220) directions were promoted both in WWS and WWOS. Fine grain size and high delta-ferrite content led to high-microhardness. The WWS had the high est microhardness among all the specimens. The WWOS and BM had a similar corrosion resistance. By comprehensive comparison, the WWS had a relative lower corrosion resistance than others, since sulfide inclusions in WWS not only had some benefits but also had some bad effects on corrosion property. (C) 2017 Elsevier B.V. All rights reserved.