Provided are a battery module, a secondary battery and a cap plate assembly. The battery module includes a plurality of secondary batteries arranged in sequence. The secondary battery includes an electrode assembly, a case and a cap plate assembly. The electrode assembly is received in the case and the cap plate assembly is connected to the case. The cap plate assembly includes a cap plate, an explosion-proof sheet and a fixing piece. The cap plate is disposed with a through hole, the explosion-proof sheet is disposed at the cap plate and seals the through hole, and the explosion-proof sheet has a weak region. The fixing piece connects the cap plate and the explosion-proof sheet. The fixing piece has a lower melting point than the cap plate and the explosion-proof sheet.