Studying　the　scale　effect　of　dynamic　airfoil　is　helpful　for　understanding　the　dynamic　stall　phenomenon　and　unsteady　wall　interference.　In　this　paper,　the　scale　effect　of　the　dynamic　stall　characteristics　of　the　dynamic　National　Advisory　Committee　for　Aeronautics　0012　airfoil　was　studied　using　time-resolved　pressure　measurements　for　the　first　time,　which　is　different　from　the　Reynolds　number　effect　as　the　experimental　Reynolds　number　was　not　varied.　The　evolution　of　the　pressure　field　and　vortex　development　characteristics　on　different　scaled　models　was　investigated.　Significant　scale　effects　were　observed　on　the　dynamic　airfoil　during　its　dynamic　stall.　With　the　model　scale　increases　from　c　=　500　to　900　mm,　the　shear　layer　vortex　and　the　secondary　separation　were　observed,　indicating　that　vortices　on　the　suction　surface　were　enriched.　Furthermore,　the　vortex-induced　suction　and　its　occurrence　time　were　significantly　affected.　The　vortex-induced　suction　varied　from　Cp　≈　-4.25　to　-1.5.　With　the　model　scale　increases　from　c　=　500　to　900　mm,　the　vortex　structure　occurrence　angle　of　attack　was　delayed　by　Δα　≈　0.5°.　Further　analyses　showed　that　the　scale　effects　of　the　dynamic　airfoil　are　attributed　to　the　flow　transition　and　unsteady　wall　interference　interactions.　Thus,　two　physical　quantities,　Sm　and　Sw,　were　innovatively　defined　to　associate　the　vortex　complexity,　model　scale,　and　wind　tunnel　wall　pressure.　This　study　helps　deepen　the　understanding　of　the　dynamic　stall　phenomenon　and　provides　guidance　for　the　unsteady　wall　interference　correction.　©　2022　Author(s).