The application relates to a top cover structure of a secondary battery, a top cover assembly and a secondary battery, which relates to the technical field of secondary batteries. The top cover structure includes: an insulating plate, provided with a lower through hole penetrating up and down; a top cover plate located on the top of the insulating plate, provided with an upper through hole interconnected with the lower through hole and penetrating up and down; a conductor, passing through the upper through hole and the lower through hole and fixedly connecting with the top cover plate and the insulating plate, and the conductor is provided with an intersecting hole penetrating through the conductor. In the present application, an intersecting hole penetrating through the conductor is provided on the conductor, so that the conductor can not only connect and conduct the secondary battery from the outside to the inside of the secondary battery, but also can conveniently inject or replenish liquid into the secondary battery through the intersecting hole, thereby improving the production efficiency of the secondary battery.