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　(Zphase)　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　gamma　Z＜0.54　gamma　H.　Our　findings　can　provide　a　novel　understanding　of　the　coercivity　mechanism　of　precipitation-hardened　Sm-Co　permanent　magnets.