Pursing　high　coercivityremanence　synergy　is　a　common　challenge　for　permanent　magnets,　particularly　for　the　La/Ce-based　REFeB　(RE:　rare　earth)　magnets　that　usually　exhibit　drastic　magnetic　dilution.　Here　we　apply　the　Pr80Ga20　grain　boundary　diffusion　process　(GBDP)　to　overcome　the　coercivityremanence　trade-off　of　the　LaCe-40　(LaCe/total　RE　=　40%)　magnet　and　yield　the　record-high　magnetic　performance　with　Hcj　=　16.1　kOe,　Br　=　13.1　kG　and　(BH)max　=　41.4　MGOe　upon　high　LaCe　substitution.　One　of　the　prominent　merits　of　the　PrGa　GBDP　is　to　assist　the　formation　of　anti-ferromagnetic　RE6Fe13Ga　phase　at　triple　junctions　and　grain　boundaries　(GBs),　which　is　observed　for　the　first　time　within　the　REFeB　diffusion　system.　The　synergetic　effects　of　Pr　to　enlarge　the　volume　fraction　of　RE-rich　phase　and　Ga　to　optimize　its　wettability　also　facilitate　the　formation　of　continuous　non-ferromagnetic　RE-rich　phase　at　GBs,　being　another　prominent　merit　of　the　PrGa　GBDP.　The　anti-ferromagnetic　RE6Fe13Ga　and　non-ferromagnetic　RE-rich　GBs　to　decouple　neighboring　ferromagnetic　matrix　grains,　and　the　Pr-rich　shell　to　strengthen　local　magnetocrystalline　anisotropy　jointly　enhance　the　coercivity,　as　demonstrated　by　the　microstructural　characterization　and　micromagnetic　simulation.　The　first　order　reversal　curve　and　Kerr　microscopy　further　reveal　the　impedance　of　the　nucleation　of　reversal　domains　in　the　PrGa　GBDP　LaCe-40　magnet,　transforming　from　multi-domain　reversal　to　single-domain　reversal.　Moreover,　Pr　infiltration　into　the　matrix　grains　increases　the　local　magnetization　and　leads　to　raised　remanence　by　0.2　kG.　The　above　work　provides　a　clear　picture　of　the　synergetic　effects　between　Pr　and　Ga　towards　fully　exploiting　paragenetic　LaCe　alloy　and　developing　the　low-cost　commercial-grade　permanent　magnets.　©　2022