The invention discloses a semi-underground large-size horizontal vacuum container for plume test research, which comprises a vacuum container, a vacuum acquiring system, a propellant supply system and a matching foundation, belongs to the field of brand-new tests, is different from the traditional ring die devices and is specially used for the plume effect test research of an engine. The semi-underground large-size horizontal vacuum container is designed into a semi-underground structure, the low-half part of the vacuum container is positioned below the horizontal plane, the vertical distance from the central axis of the vacuum container to the horizontal plane is 1.3m and is controlled to be within a range of the body height of an adult, and thus, a worker conveniently installs and maintains test devices such as an engine at the central axis in the vacuum container; and the diameter of a door is about 2.4m, the design difficulty of the door is lowered, the door is conveniently opened or closed, people enters or exits from the door, and thus, the demand of the flume test is met. The lower end of a rear saddle is fixed firmly by using a base plate and a rear bearing foundation, and thus, the radial movement of the vacuum container is avoided, and the height of the rear saddle can be regulated through the thickness of the base plate.