Diesel is one of the best hydrogen storage systems, which has very high volumetric density[kg H2/㎥] (>100) and gravimetric density[%H2] (>15). Several catalysts were selected for diesel reforming. 3 catalysts (Pt on gadolinium doped ceria, Rh and Ru on the same support, Patent for catalyst formulation of Argonne National Laboratory in U.S.A) and 2 commercial catalysts (FCR-HC14 and FCR-HC35, Süd-Chemie, Inc.) were used to reform diesel. Pt catalyst showed the best performance. Effects of operating conditions such as temperature, O2/C and H2O/C on ATR(autothermal reforming) were investigated. In addition, we studied on reaction characteristics for better understanding about ATR reaction by analyzing concentrations of products and temperature profiles along catalyst bed. We found key issues such as fuel delivery and heat transfer between front exothermic part and rear endothermic part of catalyst bed.