The utility model discloses a syringe for can be used to separate serum experiments, cover injection tube, piston push rod, piston push rod handle, rubber buffer, syringe needle including the area. The area is covered and is combined closely between injection tube and the piston push rod, and piston push rod handle fixed connection is on piston push rod upper portion, and cylinder upper portion isconnected with the lid, and the bottom of cylinder is equipped with threaded hole needle mouth to being connected with threaded hole nail, can just twisting the pinhole bottom and take screwed hole needle mouth, syringe needle has the screw thread, can just can twist and take screwed hole needle mouth bottom the cylinder, and also can combine closely. The beneficial effects of the utility model reside in that behind the extraction fish blood to can directly be used for carrying out centrifugation serum after taking away piston push rod, the experiment operation of being convenient for shifts,prevents the secondary pollution of blood transfer.