Biomass is a promising renewable energy resource. Gasification is a process that converts organic or combustible materials, such as coal, petroleum, biofuel, or biomass, into fuel gas. It is one of the methods for converting different types of fuels into gaseous fuel. The gas is composed of carbon monoxide and hydrogen and called synthesis gas or syngas. The syngas usually applicated in combustion or power generation. The gasification process requires high temperature and limited amount of oxygen and/or steam application. The steam usually used as an oxygen agent in fluidized bed gasifier for hydrogen production. The hydrogen concentration of syngas from downdraft gasification is from 10~15% in normally. In this study dried woodchip and charcoal were mixted as feedstock in a downdraft gasifier. The steam was injected from air nozzles in the gasification process when the temperature of reduction zone was higer than 700℃. The steam was heated to over 700℃ according a super steam generator. The temperature of combustion zone was decreased but the temperature of reduction zone was remaining stable at the same time. The concentration of H₂ increased more than 15% and achieved 30% in the syngas. The CO₂ concentration decreased and the CO concentration decreased in the process because of the water-gas shift reaction. High temperature of super steam makes sure the temperature of combustion zone and energy loss in the water-gas shift reaction. The Total fuel gas composition achieved nearly 50% in this process. It was presented super steam's injection improved the quality of syngas especially hydrogen composition compared to the biomass/air gasification in downdraft gasification.