The main objective of this paper is to develop a multiscale model for the simulation of heat/mass transport and electrochemical process in a solid oxide fuel cell. The model is then used to evaluate the effects of lowering the operating temperature for a solid oxide fuel cell. This model consists of two sub-models, i.e., a micro-scale sub-model and a macro-scale submodel. The macro-scale sub-model is based on the continuum conservation laws. The microscale sub-model addresses the complex relationships among the transport phenomena in the electrodes and electrolyte, which include the transport of electron, ion and gas molecules through the composite electrodes, electrolyte and three-phase boundary region. After integrating the two sub-models, the dependence of electrochemical performance on the temperature, global geometrical parameter and microstructures (porosity, volume fraction, composite ratio, etc.) were assessed. Results demonstrate that for a reduced temperature solid oxide fuel cell with composite electrodes, its performance is also lowered due to a higher ohmic loss in electrolyte and a slower electrochemical kinetics in the cathode. Among the various micro-structure parameters for electrodes, the particle size and TPB length are the most important factors that dominate the performance of a reduced temperature SOFC. In addition, optimal thicknesses for the electrodes exist. It is believed that the current work will provide a valuable model approach, which can be used to help understand the complex transport phenomena in electrodes and optimize the design of a reduced temperature solid oxide fuel cell.