A connection assembly, a connector and a connector assembly are disclosed. The connection assembly is used to connect a high-voltage cable and comprises: a threaded fastener for fixedly connecting the high-voltage cable to a mating connection part, the threaded fastener comprising an insulation member; and a conductive plug connected with the insulation member to allow the threaded fastener to be tightened or loosened by rotating the conductive plug. In the present invention, the conductive plug arranged in the mounting hole of the conductive housing can realize the electromagnetic shielding function, and the elastic sealing sleeve sleeved on the conductive plug seals the gap between the conductive plug and the inner wall of the mounting hole and can realize the waterproof function. The insulation member serves to electrically isolate the threaded connecting member from the high voltage cable.