In this work the effect of a number of HYL process parameters on direct reduced iron (DRI) quality, during a real process taking place at Suez Steel Company have been studied. These parameters are gas temperature at reactor inlet and at heater outlet, process gas flow rate, oxygen flow rate at partial combustion zone, reducing gases ratio, humidity percent in process gas, cooling gas flow rate and natural gas make-up for cooling gas. By changing these parameters, then by calculating the DRI quality (metallization and carbon content percentages ) after the residence time , I has been found that the metallization degree  increases with the increase of gas temperature at reactor inlet and at heater outlet , process gas flow, oxygen flow at partial combustion zone, reducing gases ratio, humidity percent in process gas. Also increasing of cooling gas flow rate and natural gas make-up for cooling gas has caused increase a carbon content.