Hydrogen has been recognized as the most attractive alternative and renewable energy due to consumption of gasoline and environmental concern. Ammonia decomposition provides a direct and simple route for hydrogen production since no COx and H2S are involved, which means that no water-gas shift reactors, preferential oxidation reactors and sulfur removal units are required. In this study, a MEMS reformer based on Si as a substrate material has been developed for hydrogen production from ammonia decomposition. Silica supported Pt or Ru was chosen as reforming catalyst in form of thin film and microfibrous entrapped particles, and prepared by incipient wetness impregnation. The reaction of ammonia decomposition was tested in temperature range of 200 – 600 °C. The microfibrous entrapped catalyst produced higher conversion of NH3 at all the temperatures compared to thin film catalyst, and Ru is better catalyst than Pt. For microfibrous entrapped catalysts, the experiments on different sizes of silica particles show that 20 µm silica produced higher NH3 decomposition than 40 and 60 µm particles. Ammonia conversion on microfibrous entrapped Ru reached 90% at 500 °C, and was close to 100% at 600 °C.