High-temperature phase reactions of Sr and Mg doped LaGaO3 (LSGM) electrolyte with many electrode materials including Ag, Au, Pt, Sm doped CeO2 (CSO), Sr doped LaMnO3 (LSM), and Sm doped SrCoO3 (SSCO) were investigated systematically by solid-state reaction and X-ray diffraction (XRD) analysis. Phase change and formation of minor phases were observed as a function of temperature. Single cells of LSGM electrolyte coupling with different electrode materials have been fabricated and tested by in situ ac impedance and IV curve measurement. The performance of single LSGM button cells was relative poor due to the occurrence of detrimental interfacial reactions.