The　precipitation-hardened　Sm-Co　permanent　magnets　relied　on　the　pinning　of　nanocellular　structures　to　achieve　high　coercivity,　and　have　an　irreplaceable　position　in　high-temperature　applications.　In　this　article,　by　employing　micromagnetic　simulations　and　magnetic　domain　observations,　the　pinning　behavior　of　lamellar　phases　(Z-phase)　were　investigated,　which　has　not　been　well　understood　before.　The　results　showed　that　the　Z-phase　can　serve　as　a　strong　pinning　position,　but　due　to　the　parallel　lamellar　distribution,　the　magnetic　domain　walls　can　move　around.　Additionally,　the　effect　of　Z-phase　on　coercivity　was　achieved　by　changing　the　morphology　of　magnetic　domain　walls　during　magnetization　reversal.　For　attractive　pinning,　the　coercivity　was　reduced　by　the　Z-phase,　while　for　repulsive　pinning,　the　Z-phase　increased　the　coercivity　when　γZ＜0.54γH.　Our　findings　can　provide　a　novel　understanding　of　the　coercivity　mechanism　of　precipitation-hardened　Sm-Co　permanent　magnets.　©　2024　Elsevier　B.V.