A cap assembly (100, 101, 102, 103, 104) for a secondary battery, comprising a cap plate, an electrode terminal, a fixing member (22, 32) and a connecting member, said cap assembly (100, 101, 102, 103, 104) being characterized in that: the cap plate has an electrode lead-out hole; the fixing member (22, 32) is engaged with the connecting member and the cap plate is engaged with the connecting member so that the fixing member (22, 32) is fixed to the cap plate through the connecting member; the electrode terminal comprises a terminal board (21, 31), wherein an outer peripheral surface of the terminal board (21, 31) is surrounded at least in part by the fixing member (22, 32) to fix the electrode terminal to the fixing member (22, 32), all of the electrode terminal, the fixing member (22, 32) and the connecting member are located at a side of the cap plate away from inside of a shell of the secondary battery, wherein one of the terminal board (21, 31) and the fixing member (22, 32) is provided with a convex portion, and the other is provided with a concave portion that accommodates the convex portion, and the concave portion and the convex portion are fitted with each other to fix the terminal board (21, 31) to the fixing member (22, 32), wherein the terminal board (21, 31) covers the electrode lead-out hole, and the outer peripheral surface of the terminal board (21, 31) protrudes out of an inner wall of the electrode lead-out hole, wherein the cap assembly (100, 101, 102, 103, 104) further comprises a sealing member (23, 33), wherein the sealing member (23, 33) contacts with the terminal board (21, 31) and is disposed between the terminal board (21, 31) and the cap plate to seal the electrode lead-out hole, wherein the connecting member comprises a first connecting plate made of a metal material, the first connecting plate comprises an engagement portion and a contact portion connected with the engagement portion, the fixing member (22, 32) comprises a notch, the engagement portion is inserted into the notch and engaged with the fixing member (22, 32), the contact portion is exposed out of the notch and contact with the cap plate. the cap plate has an electrode lead-out hole; the fixing member (22, 32) is engaged with the connecting member and the cap plate is engaged with the connecting member so that the fixing member (22, 32) is fixed to the cap plate through the connecting member; the electrode terminal comprises a terminal board (21, 31), wherein an outer peripheral surface of the terminal board (21, 31) is surrounded at least in part by the fixing member (22, 32) to fix the electrode terminal to the fixing member (22, 32), all of the electrode terminal, the fixing member (22, 32) and the connecting member are located at a side of the cap plate away from inside of a shell of the secondary battery, wherein one of the terminal board (21, 31) and the fixing member (22, 32) is provided with a convex portion, and the other is provided with a concave portion that accommodates the convex portion, and the concave portion and the convex portion are fitted with each other to fix the terminal board (21, 31) to the fixing member (22, 32), wherein the terminal board (21, 31) covers the electrode lead-out hole, and the outer peripheral surface of the terminal board (21, 31) protrudes out of an inner wall of the electrode lead-out hole, wherein the cap assembly (100, 101, 102, 103, 104) further comprises a sealing member (23, 33), wherein the sealing member (23, 33) contacts with the terminal board (21, 31) and is disposed between the terminal board (21, 31) and the cap plate to seal the electrode lead-out hole, wherein the connecting member comprises a first connecting plate made of a metal material, the first connecting plate comprises an engagement portion and a contact portion connected with the engagement portion, the fixing member (22, 32) comprises a notch, the engagement portion is inserted into the notch and engaged with the fixing member (22, 32), the contact portion is exposed out of the notch and contact with the cap plate.