The present invention discloses a simulation device and an experiment for oil-gas-brine migration law research in a salt cavern. The simulation device comprises a long core holding unit, a booster pump, a first high-pressure cavity, a second high-pressure cavity and a hydraulic pump; the booster pump communicates with a first end of the first high-pressure cavity and a first end of the second high-pressure cavity through a first pipeline; the booster pump communicates with a first end of the long core holding unit through a second pipeline; a second end of the first high-pressure cavity and asecond end of the second high-pressure cavity communicate with the second pipeline through a branch pipe; the hydraulic pump communicates with the first pipeline through a third pipeline; and a secondend of the long core holding unit communicates with a collection device through a fourth pipeline. The simulation device employs air pressure or hydraulic pressure to compress a testing medium into the high-pressure cavities to allow the testing medium to flow into a lone core, and pressure sensors arranged along the way are employed to achieve real-time monitoring of a pressure transmission andevolution process.