In　order　to　ensure　the　safety　and　reliability　of　weapons,　it　is　very　important　to　grasp　the　influence　of　the　inside　and　outside　diameters　of　the　shell　on　the　delay　time.　In　this　paper,　a　fluid-solid　coupling　model　is　established　for　a　metal　baffle-type　delay　element　with　a　silicon-based　delay　composition.　The　combustion　flow　field　of　the　delay　element　with　the　inside　diameter　of　3,　4,　and　5　mm　is　simulated　by　the　Star-CD　software.　Then　a　new　method　is　proposed　to　calculate　the　delay　time　of　the　heat　conduction　delay　element.　The　influence　of　the　internal　and　external　diameters　on　the　delay　time　of　the　thermal　conduction　delay　element　is　studied.　The　results　show　that　the　temperature　of　the　ignition　composition　gradually　increases　due　to　the　heat　conductivity　of　the　metal　baffle　after　burning　of　the　delay　composition,　and　the　highest　temperature　is　reached　at　the　centre　of　the　ignition　composition.　The　influence　of　the　size　of　the　inside　and　outside　diameters　on　the　delay　time　has　a　critical　equilibrium　point,　which　may　be　related　to　the　balance　between　the　combustion　heat　increment　and　the　heat　loss.