Preparation of the thin film La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ (LSGM) on a porous La_0.7Sr_0.3MnO₃ (LSM) substrate using the sol-gel method was investigated. At first, a stable precursor solution was prepared. Then the thin films were prepared from the solution by spin coating on a porous LSM substrate filled with ethylene glycol. The phase of the obtained films was confirmed by X-ray diffraction. Main phase of the films was LSGM and a small amount of impurity phases was detected. The thickness of the prepared films was about 2μm, which is measured by Scanning Ion Microscopy (SIM). The good adherence of the thin films to the porous substrate was observed.