The invention discloses a novel closed thoracic drainage trocar, which comprises a telescopic protective head and a drainage sleeve, wherein a ball head is arranged at the front end of the telescopicprotective head and the front end of the telescopic protective head extends out of a conical cutting tube; the conical cutting tube is connected to the drainage sleeve; a drainage tube baffle part isarranged at the back end of the drainage sleeve; a limiting plate is arranged at the back end of the conical cutting tube, and the bottom is connected to a spring; the other end of the spring is fixedto a fixed plate which is designed in the drainage sleeve; an inclined clamping plate is fixed to the inner wall of the drainage sleeve; a clamping block is arranged at the back of the front end of the inclined clamping plate; and the clamping block is arranged in the telescopic protective head. The novel closed thoracic drainage trocar provided by the invention has the advantages of being high in safety, free from such complications as lung tissue secondary injury, accentuated haemorrhage and the like, low in patient's injury, light in complications, rapid in postoperative recovery and freefrom infection.