The disclosure relates to a cap assembly and a secondary battery. The cap assembly includes: a cap plate including a main portion and a convex portion, the main portion including a first surface, a second surface and an electrode lead-out hole; an electrode terminal including an extension portion that extends beyond a hole wall of the electrode lead-out hole and extends in a circumferential direction of the electrode lead-out hole to form a ring structure, and the extension portion is arranged on a side of the first surface away from the second surface; and a sealing ring at least partially disposed between the extension portion and the main portion. The convex portion is disposed on the second surface and around the electrode lead-out hole, and a top surface of the convex portion extends out of the second surface.