Disclosed is a mating structure of a liquid extraction piece and a test tube assembly which comprises the liquid extraction piece (1) and the test tube assembly (4). A test tube plug (2) is arranged at an opening end (32) of a test tube (3). The lower portion of the liquid extraction piece (1) is mated with the test tube assembly (4). The body of the test tube plug (2) is provided with a blocking body (25). The blocking body (25) is provided with a movable portion (253) and a fixed portion (252). The movable portion (253) can move with respect to the fixed portion (252). An axial recess is arranged above an upper surface (251) of the movable portion (253). The lower portion of the liquid extraction piece (1) is mated with the recess. The blocking body (25) is located in a lumen (31) of the test tube (3).
