This study discusses about butane autothermal reforming for small scale reactor, especially by using microchannel catalyst. By mass transfer limitation, fuel conversion seriously decreases when GHSV (gas hourly space velocity, /h) increases in a packed bed reactor. In a monolith catalyst reactor, fuel conversion behavior shows dependence on catalyst thickness on the monolith and GHSV. It was mainly attributed to diffusion velocity difference between internal mass transfer and external mass transfer of catalyst particle. Significant performance improvement in metal mesh substrate was obtained compared with a packed bed.