The invention discloses a thermal insulation layer assembly suitable for an aluminum alloy long tail spraying pipe solid rocket engine. The thermal insulation layer assembly comprises a front end socket thermal insulation layer, a combustion chamber thermal insulation layer, a spraying pipe thermal insulation layer, a throat lining, an expansion section thermal insulation layer and other parts. The whole thermal insulation layer assembly is in a rigid totally-coated type structural form. The front end socket thermal insulation layer is connected with the combustion chamber thermal insulation layer through an L-shaped lap joint structure. The combustion chamber thermal insulation layer is connected with the spraying pipe thermal insulation layer through an L-shaped lap joint structure. Thespraying pipe thermal insulation layer is connected with the expansion section thermal insulation layer through an L-shaped lap joint structure. By means of the rigid totally-coated type thermal insulation layer assembly, the impulse to mass ratio and work reliability of the rocket engine are increased, the preparing time of the thermal insulation layer assembly is shortened, the redundant mass ofthe rocket engine is reduced, batched production is easy, quality consistency is high, assembling can be completed only with one assembling worker, and the thermal insulation layer assembly is suitable for aluminum alloy solid rocket engines with the diameter of 200.00 mm or below and the long tail spraying pipe length of 150.0 mm or below.