The invention discloses a test tube and a method applied to saliva DNA centrifugal pretreatment. The test tube comprises a test tube body, a test tube cap and a seal cap, wherein a protrusion around the periphery of the bottom of the test tube body is arranged at the bottom of the test tube body or a protrusion around the tube wall of the test tube body is arranged at the lower portion of the test tube body, and a seal connection mechanism is arranged at the tube opening position of the test tube body; the test tube cover is matched with and in seal connection with the seal connection mechanism through a seal connection mechanism, and the cells which are obtained from centrifugal treatment and contain the saliva DNA can precipitate in the test tube cap when the centrifugal treatment is performed with the pipe opening of the test tube body downward; the seal cap is matched with and in seal connection with the seal connection portion through a seal connection structure, and the test tube cap can be sealed to be used for storing the cells which are obtained from centrifugal treatment and contain saliva DNA. The saliva DNA is concentrated into a half-solid state which is small in size and stored in the test tube cap and the seal cap, the carrying size is small, great convenience is brought to storage and transportation of saliva samples in a room temperature, and the DNA quality isn't affected.