Abstract: A triaxial test device for deep-sea coring retaining in-situ condition suitable for a shipborne laboratory, includes a sample transfer system and a triaxial machine system. The sample transfer system includes a sample cylinder, a tube-removing piston, a ball valve, and a connector, the sample cylinder is connected to the ball valve through bolts, the sample is placed in the sample cylinder, and the tube-removing piston arranged in the sample cylinder is configured to push the sample to enter the triaxial machine system. The triaxial machine system includes a bottom interface, a rubber cylinder, a triaxial inner wall, a triaxial outer wall, and a top interface; the bottom interface is hermetically connected to the sample cylinder through the connector, the bottom interface communicates with the rubber cylinder arranged in an inner cavity of the triaxial inner wall, the sample is sent into the rubber cylinder for a triaxial compression test.