Disclosed is a catalyst used for steam carbon dioxide reforming of natural gas, wherein an alkaline earth metal alone or an alkaline earth metal and a group 8B metal are supported on a hydrotalcite-like catalyst containing nickel, magnesium and aluminum. The disclosed catalyst is useful as a steam carbon dioxide reforming (SCR) catalyst of natural gas at high temperature and high pressure, while minimizing deactivation of the catalyst due to sintering of the active component nickel and deactivation of the catalyst due to coke generation at the same time. A synthesis gas prepared using the catalyst has a H2/CO molar ratio maintained at 1-2.2. A synthesis gas having a H2/CO molar ratio of 1.8-2.2 may be used as a raw material for Fischer-Tropsch synthesis or methanol synthesis and a synthesis gas having a H2/CO molar ratio of may be used as a raw material for dimethyl ether synthesis.