We have developed a new Ni-Cr alloy adding Si and Cu which are effective to resist metal dusting corrosion at intermediate temperatures. We conducted long-term laboratory test in a simulated syngas environment at 575-C to investigate an influence of temperature. In addition we tried to evaluate the metal dusting resistance of the new alloy in commercial GTL plants where the gas atmosphere is severe carbonaceous environment. In this paper we present that the both tests have been successfully completed i.e. the new alloy has no metal dusting attack.