Reducing the operational temperature for high-temperature solid oxide fuel cell (SOFC) is of great significance to improve the stability of materials, increase the operation life of the system and reduce the fabrication and operation cost of the cell. This aspect has therefore attracted recent research attention. So far, different research strategies were proposed to reduce the operational temperature. This review represented recent research progress on the composite electrolyte in low-temperature solid oxide fuel cell (LT-SOFC). The carbonate materials as the second phase for composite preparation of molten carbonate-like SOFCs and the transition metal oxide materials as the second phase for composite preparation were introduced. The single-component fuel cell for eliminating the interface resistance between electrode and electrolyte and improving the fuel cell performance and the stability of the peroxide composite electrolyte was elaborated. The semiconductor composites to enhance LT-SOFC's electrochemical performance were described. In addition, this review also represented the preparation of novel nanocomposites to further enhance the electrolyte ionic conductivity and the interfacial compatibility, and the explorations of the electrochemical performance of LT-SOFC with respect to the effect of novel electrode materials.