This study detects the resistance that influences the stack performance of SOFCs with composition of NiYSZ/YSZ/LSC-YSZ and investigates the variation patterns of the resistances of the stack repeating unit (SRU) during operation and their quantitative contributions to its performance at 700 degrees C, 750 degrees C and 800 degrees C. The results indicate that when the cell cathode contacts the interconnect well, the cell resistance accounts for 70.1-79.7% of that of the SRU, and the contact resistance (CR) between the cathode current-collecting layer (CCCL) and the interconnect accounts for 20.0-28.9%. The CR between the anode current-collecting layer (ACCL) and the interconnect together with the resistance of the interconnect can be neglected during instantaneous I V testing. When the stack is discharged at constant current for 600 h, cell resistance increases by 28.3%, accounting for 93.3% of the SRU degradation, the anodic CR increases by 36.4%, accounting for 6.7% of the SRU degradation, and the resistances of the cathode contact and its neighbor interconnect remain unchanged. Therefore, the increase of the cell resistance is the main reason causing the SRU degradation, and the anodic contact is also an influencing factor that cannot be neglected during stable operation. (C) 2013 Elsevier B.V. All rights reserved.