in a continuousflow microreactor. The Co content has a significant effect on the activity of the cobalt-magnesium oxide solid solution catalysts. The catalysts containing 5 and 10% Co have the lowest light-off temperature in methane combustion. In the preparation of cobalt-magnesium oxide solid solution catalysts, higher urea to metal ratio favors the formation of the catalysts with smaller crystal particles and leads to a better catalytic performance for methane combustion. Addition of lanthanum nitrate to the solution of Co and Mg nitrate depressed the formation of the cobaltmagnesium oxide solid solution and decreased the activity of the catalysts for methane combustion. The cobalt-magnesium oxide solid solution catalysts are very stable when the calcination or reaction temperature is no more than 900◦C. However, the catalytic activity decreases rapidly after high temperature (>1000℃) calcination, possibly due to sintering of the catalyst and thus decrease of the surface area.