A new configuration of a micro reforming system integrated with a micro-combustor is studied experimentally and computationally. The micro-combustor as a heat source is a simple cylinder, which is easy to fabricate, but is two-staged (expanding downstream) to control ignition and stable burning. A micro-evaporator to vaporize methanol-water mixtures and a micro-refonner to convert the vaporized methanol-water mixtures to hydrogen are annuli, which are effective to transfer heat from the first and second-stage micro-combustors, respectively. The annulus-type micro reforming system is designed to produce 1-10 W (based on lower heating value, LHV) of hydrogen using the steam reforming method. The molar ratio of water to methanol, the feed rate of water-methanol mixtures, the micro-combustor inlet velocity of fuel-air mixtures and the micro-combustor materials substantially affect the performance of the designed micro reforming system. Under optimized design and operating conditions, the micro reforming system produces 6.9 W (based on LHV) of hydrogen with a conversion rate of 97.5%, an overall system efficiency of 39.7% and a carbon monoxide concentration of 6.7 ppm. Thus, the present configuration can be applied to practical micro reforming systems for use with fuel cells. (c) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.