The invention discloses a variable structure type C type LNG (liquefied natural gas) liquid tank oscillation test system, and belongs to the oceanographic engineering LNG/LPG (liquefied petroleum gas) storage and transportation technology field. The variable structure type C type LNG liquid tank oscillation test system is composed of an end socket, a main tank body, a swash bulkhead, an oscillation simulation platform, a control system and the like. A test tank is divided into three portions which are respectively a first end socket, a second end socket and the main tank body. The first end socket and the second end socket are installed at two ends of the main tank body. The swash bulkhead is fixed in the test tank, and placed at an optional position in the main tank by loosening and tightening a coupling screw on the swash bulkhead. Pressure sensors are arranged on designated positions in the test tank, on the end socket and on the swash bulkhead, and wireless signals and wired signals, sent by the pressure sensors, are received by the control system. The variable structure type C type LNG liquid tank oscillation test system has the advantages of being capable of testing influences of different forms of the end sockets on oscillation physical properties, using a dismountable combination mode, being convenient to install, dismantle and maintain, facilitating position and quantity adjustment of the swash bulkhead and form replacement of the swash bulkhead, and improving flexibility of a test.