Abstract: The causes and the influence factors of porosity in the weld of self-shieldedflux-cored wire (SSFCW) were studied through providing different gaseous stream flow into arc area and determining the content of oxygen, nitrogen and hydrogen in deposit metal. As it turned out: that oxygen and nitrogen content are main influence factors for formation of porosity in the weld of SSFCW, oxygen can rapidly increase the quantity of porosity in the weld of SSFCW and hydrogen content is not of the main influence factors of the porosity formation in the weld of SSFCW.