A combustor, in which a flame holding region is formed at a location distant from a pilot burner to avoid burnout of the pilot burner and in which flame holding capability is increased to use a lean pre-mix gas for reducing NOx emission, is provided. The combustor includes a combustion liner having a cylindrical side wall that defines a combustion chamber; and a main burner positioned at a top portion of the combustion liner for injecting an annular pre-mix gas into the combustion chamber to form a reverse flow region at a downstream portion thereof, which region is oriented towards the top portion of the combustion chamber along a longitudinal axis. In this combustor, a pilot burner is arranged at the top portion for injecting a mixture of fuel and air only in a direction confronting the reverse flow region.