This research studies for improvement of produced hydrogen by 1. theoretical study of combined biomass gasification with tar steam reforming and 2. experimental study for suitable catalytic and condition of tar steam reforming reaction. First, Thermodynamic analysis reveals that when selecting appropriate operating conditions, exothermic heat available from the gasifier could sufficiently supply to the heat-demanding units including feed preheaters, steam generator and reformer. The effects of gasification temperature (Tgs), reforming temperature (Tref) and steam-tobiomass ratio (S:BM) on percentages of tar removal and improvement of H2 production were investigated. It was reported that the CGR system can completely remove tar and increase H2 production (1.6 times) under thermally self-sufficient condition. The increase of H2 production is mainly via the water–gas shift reaction. The experimental study of the tar steam reforming reaction were carried out at different temperatures (450-650 ๐C), S/C ratios (1-5), type of supports (Al2O3, CaO, MgO) and %metal loading of a nickel catalyst. Representative tar consisted of toluene, naphthalene, phenol and pyrene whose compositions varied with temperatures of biomass gasification (700-900 ๐C). The experimental results follow the trends observed from the simulations that the reaction at high temperature and S/C ratio produce more hydrogen content. 20%Ni/Al2O3 was reported as a suitable catalyst which offered stable and efficiency activity for tar steam reforming.