Vulcanization　molding　has　a　significant　impact　on　dimensional　changes　of　rubber　seals.　Numerical　analysis　of　this　process　can　improve　dimensional　accuracy　of　molded　sealing　products.　In　this　study,　a　stress–strain　relationship　model　that　considers　thermal　expansion,　cold　contraction,　and　shrinkage　caused　by　a　crosslinking　reaction　under　the　constraint　of　a　mold　boundary　was　established,　a　transient　analysis　method　for　thermal–mechanical–chemical　coupling　of　the　process　from　rubber　seal　vulcanization　to　mold　opening　was　developed,　and　dimensional　changes　of　the　rubber　seal　in　the　mold　and　after　cooling　were　predicted.　Results　calculated　by　the　model　were　verified　by　the　production　of　typical　seals.　The　influences　of　vulcanization　process　parameters　on　changes　in　molded　seal　size　were　numerically　analyzed.　The　numerical　results　showed　that　the　dimensional　shrinkage　ratio　increased　nonlinearly　from　3.2　%　to　3.8　%　when　the　vulcanization　temperature　increased　from　165　to　185　°C,　i.e.,　an　increase　of　0.206　%　for　every　1　%　increase　in　shrinkage　caused　by　the　vulcanization　reaction.　These　research　results　can　be　utilized　in　the　design　of　vulcanization　molds　for　high-precision　rubber　seals.　©　2022　The　Authors