The invention discloses a step type inspection well structure for a thermal insulation center trench below a tunnel inverted arch. The step type inspection well structure comprises a deep-buried center trench thermal-insulation inspection well and a deep-buried tunnel center trench, wherein the deep-buried center trench thermal-insulation inspection well is equipped with lateral step ladders from top to bottom in the longitudinal direction of a path, the lower ends of the lateral step ladders are connected with the deep-buried center trench thermal-insulation inspection well through maintenance platforms, and open holes capable of allowing implementation of inspection and maintenance work for the deep-buried tunnel center trench through the deep-buried center trench thermal-insulation inspection well are formed in the positions, corresponding to the maintenance platforms, of the deep-buried center trench thermal-insulation inspection well; cover plates are arranged at the tops of the lateral step ladders for closing, and an oil-immersed wood cover plate and a thermal-insulation layer are arranged in the position, having equal altitude with the top surfaces of the maintenance platforms, of the deep-buried center trench thermal-insulation inspection well for closing and thermal insulation. According to the step type inspection well structure for the thermal insulation center trench below the tunnel inverted arch, concrete project quantity of the tunnel bottom structure is reduced, cold-proof and thermal-insulation capacity of a tunnel drainage system is improved, and operation difficulties in inspection and maintenance of deep-buried drainage facilities of the tunnel are reduced, so that the operation safety of the tunnel is guaranteed.