We have developed a highly porous platinum-alumina cryogel catalyst for exhaust gas purification with high activity and superior thermal stability. The reaction temperature of this catalyst is lower by about 100ºC than that of conventional catalysts, and the thermal resistance has been improved to approximately 200ºC. The advantage of this catalyst, together with the use of low cost aluminum hydroxide as the starting material, and the implementation of a low cost and simple process such as freeze-drying, will lead to the spread of its applications.