GaN/AlN　two-layer　films　with　different　thickness　are　synthesized　on　Si　substrates　by　pulsed　laser　deposition　(PLD).　GaN　and　AlN　single-layer　films　are　also　synthesized　for　comparison.　It　is　found　that　the　turn-on　field　of　the　GaN/AlN　twolayer　films　are　considerably　decreased　2　orders　of　magnitude　than　that　of　single-layer　films.　The　improvement　of　FE　characteristics　an　attributed　to　the　quantum　structure　effects,　which　supplies　a　favorable　location　of　electron　emission　and　enhances　tunneling　ability.　We　show　that　by　tuning　the　thickness　of　GaN/AlN,　various　FE　characteristics　can　be　obtained,　which　is　induced　by　the　modulation　of　quantum　potential　well/barrier　structure.　It　indicates　that　an　optimal　thickness　exists　for　GaN/AlN　two-layer　nano-films　to　give　best　field　emission　performance.　©2010　IEEE.