The present disclosure provides a cap assembly for a secondary battery and a secondary battery. The cap assembly for the secondary battery includes a cap plate having an electrode lead-out hole; and a terminal assembly including a terminal board, a fixing member, a deformable sheet, a conductive sheet and an isolator, wherein the deformable sheet is attached to the terminal board; the conductive sheet includes a first portion provided between the terminal board and the cap plate; the terminal board is fixed to a side of the cap plate through the fixing member and covers the electrode lead-out hole, and the terminal board is electrically connected with the first portion through the deformable sheet; the deformable sheet is configured to deform to be electrically disconnected from the first portion in response to an increase in a pressure inside the secondary battery.