The invention discloses an unequal-thickness heat-insulating layer of a horizontal thermal pipeline and a manufacturing method of the unequal-thickness heat-insulating layer. The heat-insulating layer of the thermal pipeline is in bilateral symmetry; the right half of the heat-insulating layer of the thermal pipeline is divided into n sections at angle intervals of alpha from the top to the bottom, wherein n is equal to Pi/alpha; the included angle between the center line of the ith section and the top of the thermal pipeline is theta i, and i is greater than or equal to 1 and smaller than or equal to n; the thickness of the heat-insulating layer of the ith section is delta i. The unequal-thickness heat-insulating layer saves materials, and through local regulation of the thickness of the heat-insulating layer material, the heat-insulating effect of the unequal-thickness heat-insulating layer is improved, so that the heat-insulating effect is improved on the premise that the total amount of the heat-insulating material is not increased; compared with the conventional method for improving the heat-insulating effect by increasing the thickness of the heat-insulating layer, the manufacturing method has the advantage of saving more materials; in design, the influence of sinking deformation of the heat-insulating layer is considered; the unequal-thickness heat-insulating layer is high in practicality; extra equipment is not required; the heat-insulating effect can be improved only by regulating the heat-insulating thickness distribution of a local position.