The small polymer electrolyte fuel cell (PEFC) was experimented by changing operation temperature and H-2 and O-2 concentration in supply gas, and the PEFC reaction characteristic model that can express these influences was created. Moreover, PEFC reaction and flow analysis model was made with this reaction characteristic model and thermal flow analysis model. Furthermore, in order to improve the performance and the safety of PEFC, five kinds of separators were evaluated from the viewpoint of state of gas flow, uniformity of current density and temperature, reduction of pressure loss and exhaustibility of liquid water with this PEFC reaction and flow analysis model. In case of parallel separator, flow rate and current density distribution was not uniform, and exhaustibility of the liquid water was low. In case of serpentine separator, pressure drop was large. In addition, semi-serpentine separator was designed for the shape which combines parallel separator and serpentine separator, and the temperature and current density distribution of this separator was more uniform than any other separators, so this separator was excellent. (c) 2005 Elsevier B.V. All rights reserved.