In this paper, basic studies on the high temperature steam gasification system which is named as HyPR-MEET system were carried out using the Japanese cedar and pure polyethylene (PE) particles as feedstocks. First, the characteristic of steam gasification is investigated. With each feedstock, the hydrogen concentration increases as the gasification temperature rises, but the increase rate of the hydrogen concentration decreases over the temperature of 1073K for Japanese cedar and 1173K for PE. The increase of the steam/carbon molar ratio also increases the hydrogen concentration. Second, the effectiveness of the Ru/Al 2 O 3 catalyst for steam reforming of tar components is investigated. With use of this catalyst, tar components can be reformed at the temperature of 973K, while the temperature of 1173K is required without use of any catalysts. Furthermore, light hydrocarbon gases are also reformed with this catalyst, and the hydrogen concentration in the reformed gas can reach the value of 55% for Japanese cedar, and of 68% for PE.