The invention provides a temperature control box for an online chromatographic analyzer. The temperature control box comprises a liner, a chromatographic column, a thermal insulation material, a metal reinforcing piece, a heat source and a temperature-sensing component, wherein the chromatographic column is inlaid on the outer surface of the liner; the outer diameter of the liner is equal to the inner diameter of the chromatographic column; the thermal insulation material is coated on the outer surface of the chromatographic column; the metal reinforcing piece is a shell made of a metal material at the periphery of the thermal insulation material and is used for reinforcing the inner thermal insulation material and the liner; the distance between the heat source and the temperature-sensing component is 5mm; the heat source and the temperature-sensing component are arranged in the liner and are respectively connected to a control circuit board outside the temperature control box through a connecting line. The temperature control box is small in size, low in energy consumption, small in noise, high in temperature control precision and wide in application environment.