A cap assembly for a secondary battery, characterized by comprising a cap plate, a first electrode terminal, a sealing member (23, 33), a fixing member (22, 32) and a connecting member, wherein: the cap plate has an electrode lead-out hole to enable electrical connection between the first electrode terminal and an electrode assembly inside a shell of the secondary battery; the first electrode terminal is located at a side of the cap plate away from inside of the shell of the secondary battery, the first electrode terminal comprises a first terminal board and a second terminal board connected with the first terminal board, wherein the first terminal board is located at a side of the second terminal board away from the cap plate, the second terminal board covers the electrode lead-out hole, and the material of the first terminal board and the material of the second terminal board have different base metals, wherein a base metal of a material is the main metal in a composition of the material; the sealing member (23, 33) surrounds the electrode lead-out hole and is disposed between the cap plate and the first electrode terminal to seal the electrode lead-out hole, wherein one portion of the connecting member is fixed to a surface of the cap plate at a side of the cap plate away from the inside of the shell of the secondary battery and another portion of the connecting member is engaged with the fixing member (22, 32), the fixing member (22, 32) is fixed to the cap plate through the connecting member, and an outer peripheral surface of the first electrode terminal is at least partially surrounded by the fixing member (22, 32) to fix the first electrode terminal to the fixing member (22, 32). the cap plate has an electrode lead-out hole to enable electrical connection between the first electrode terminal and an electrode assembly inside a shell of the secondary battery; the first electrode terminal is located at a side of the cap plate away from inside of the shell of the secondary battery, the first electrode terminal comprises a first terminal board and a second terminal board connected with the first terminal board, wherein the first terminal board is located at a side of the second terminal board away from the cap plate, the second terminal board covers the electrode lead-out hole, and the material of the first terminal board and the material of the second terminal board have different base metals, wherein a base metal of a material is the main metal in a composition of the material; the sealing member (23, 33) surrounds the electrode lead-out hole and is disposed between the cap plate and the first electrode terminal to seal the electrode lead-out hole, wherein one portion of the connecting member is fixed to a surface of the cap plate at a side of the cap plate away from the inside of the shell of the secondary battery and another portion of the connecting member is engaged with the fixing member (22, 32), the fixing member (22, 32) is fixed to the cap plate through the connecting member, and an outer peripheral surface of the first electrode terminal is at least partially surrounded by the fixing member (22, 32) to fix the first electrode terminal to the fixing member (22, 32).