Sr-doped LaMnO3 and Yttria stabilized zirconia (LSM-YSZ) composite powder is synthesized by the preparation of LSM on submicron-sized YSZ particles using an in-situ glycin-nitrate combustion method for solid oxide electrolysis cells (SOEC) in this paper. LSM-YSZ composite powder and the relevant LSM powder are characterized by XRD and FESEM. The results show that LSM-YSZ is net-porous composite powder while YSZ and LSM do not react with each other during synthesis process. The electrochemical test of the single button cells indicates that the in-situ LSM-YSZ powder shows better electrolysis performance and lower discharging capability than traditionally direct mixture LSM and YSZ oxygen electrode. When operating in SOEC mode with constant current electrolysis at a Current density of 0.33 Acm(-2) and 900 C, the electrolytic voltage decreases from 1.21 V to 1.02 V, which indicates that LSM-YSZ electrode has an activation process at the initial testing stage. A mechanism which involves the incorporation of SrO segregated on the surface into the LSM lattice and the generation of oxygen vacancies in the LSM electrode is proposed for the activation process with O2- oxidation on LSM electrodes. (C) 2009 Elsevier B.V. All rights reserved.