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In order to further reduce CO2 emission in ironmaking, utilization of a large amount of hydrogen to a blast furnace would be essential in the future. In this work, influence of hydrogen half substitute to bosh gas on reaction behavior of sinter under a blast furnace simulated condition was examined until 1400℃ using a laboratory reactor. In the reactor with electric heating parts, two pieces of sinter (15mmφx10mm size) were set inside a graphite crucible (18mm inner dia.) and heated up under 1 kg load until 1400℃ according to a heating pattern with a thermal reserve zone temperature 1000℃ in gas flow conditions with or without hydrogen half substitute to basic bosh gas N2-CO-CO2. Reduction of sinter finalized around 1100℃ in the condition of H2 substitute, while the reduction retarded around these temperatures in the condition without H2 substitute, being likely because low melting slag containing residual FeO was formed due to weaker reduction power of CO than hydrogen. The condition of H2 substitute provided higher carbon contents in sinter after reduction than the condition without H2 substitute. This is likely because hydrogen promoted carburization to solid iron with CO gas and provided more amounts of reduced irons. The condition of H2 substitute improved softening melting behavior of sinter by nearly 70℃, being likely because the condition inhibited the formation of the low melting slag. Furthermore, from analysis based on List model it was evaluated that an operation with half substitute of hydrogen to a basic bosh gas gave less coke rate 346 kg/thm and less BF production 7945 t/day compared with 461kg/thm and 8999 t/day in a basic operation. The results will be overall compared and discussed to aim at an innovative high productivity with H2 half substitute to bosh gas in a blast furnace.