In this study, a typical three-dimensional model of single channel mono-block-layer build solid oxide fuel cell (MOLB-type SOFC) was developed. The effects of rib width and cathode thickness on the species concentration distribution, electrochemical performance, and temperature distribution of MOLB-type SOFC were investigated. The results show that adapting a smaller rib width can improve the uniformity of gas distribution, decrease the concentration polarization, and improve the output performance of SOFC. The performance of the cell can be significantly improved by thickening the cathode electrode. When the cathode thickness is 0.45 mm, the maximum output power density is improved by 53.69% compared with that at 0.15 mm. With the increase of the cathode thickness, the enhancement of the cell performance by increasing the cathode thickness gradually decreases. In addition, as the cathode thickness increases, the concentration polarization and temperature gradient of the cell gradually rise, while the activation polarization gradually decreases.