The invention discloses a tension test apparatus of a concrete-filled steel tube used in deep sea under a confining pressure condition. The apparatus comprises an upper clamping device and a lower clamping device, two ends of a test piece to be tested are respectively clamped by the upper clamping device and the lower clamping device, the test piece to be tested is sequentially provided with at least one confining pressure device along the axis, every confining pressure device comprises a left confining pressure cover semicircular cylinder and a right confining pressure cover semicircular cylinder, the left confining pressure cover semicircular cylinder and the right confining pressure cover semicircular cylinder sleeve the test piece to be tested through connecting devices, the left confining pressure cover semicircular cylinder and the right confining pressure cover semicircular cylinder are provided with cavities, the cavities are connected with an oil conveying tube through oil guiding holes, and the oil conveying tube is connected with a hydraulic tube. The tension test apparatus of a concrete-filled steel tube used in deep sea under a confining pressure condition allows the test piece to be tested to undergo tension test under the adjustment of the confining pressure, can carry out different oil pressure tests on the test piece to be tested, and accords with the practical bearing condition of the concrete-filled steel tube used in deep sea.