The utility model discloses a low energy consumption auxiliary combustion chamber, which is characterized in that a first main air inlet valve and a second main air inlet valve are arranged on a main air inlet pipeline communicated with the auxiliary combustion chamber, the outlet of the auxiliary combustion chamber is communicated with a reactivator of a catalytic cracking unit through a reactivator leveling pipe, a by-path air inlet pipeline communicated with the outlet of the auxiliary combustion chamber is arranged on the main air inlet pipeline, and a by-path air inlet valve is arranged on the by-path air inlet pipeline. When the auxiliary combustion chamber supplies heat to the reactivator, the by-path air inlet valve is closed; and after the reactivator of the catalytic cracking unit gets into the normal running, the auxiliary combustion chamber stops supplying heat to the reactivator, and the by-path air inlet valve is opened, so that dominant wind from the outside can directly enter the reactivator of the catalytic cracking unit through the main air inlet pipeline and the by-path air inlet pipeline, thereby reducing the pressure drop of the dominant wind, decreasing the energy loss, reducing the power consumption of a main air blower, saving the energy, and lowering the production cost. The auxiliary combustion chamber provided by the utility model can be popularized and used on a catalytic cracking unit of oil refining equipment.