Nanostructured　AIN/GaN　films　with　different　thickness　are　synthesized　on　Si　substrates　by　pulsed　laser　deposition　(PLD).　GaN　and　AIN　single-layer　films　are　also　deposited　for　comparison.　It　is　found　that　the　turn-on　field　of　the　nanostructured　AIN/GaN　films　is　considerably　decreased　2　orders　of　magnitude　than　that　of　single-layer　films.　The　improvement　of　field　emission　(FE)　characteristics　is　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　AIN/GaN,　various　FE　characteristics　can　be　obtained.　It　indicates　that　the　optimal　thickness　of　the　nanostructured　AIN/GaN　films　exists　for　their　best　field　emission　performance.