This study investigated hydrogen produced by feeding rice straw into a microwave plasma system. The conversion rate is evaluated according to the concentration of hydrogen and other gas products. When feed rice straws into the microwave plasma system at 800 W, 900 W, and 1000 W using an upstream method, the concentrations of hydrogen production were 48%, 53%, and 56%, respectively. When feed rice straws by using the downstream method, the concentrations of hydrogen production are 34%, 40%, and 45%, respectively. These results indicate that the upstream feeding method is more favorable than the downstream for hydrogen production, and an increase of power can enhance the production of hydrogen. Optimal hydrogen production is achieved when rice straws are fed into the system using the upstream method at a power of 1000 W; each gram of rice straw produced approximately 40.47 mg of hydrogen (conversion rate = 67.45%). (C) 2013 Elsevier Ltd. All rights reserved.