©　2016,　Editorial　Board　of　Journal　of　Xi＇an　Jiaotong　University　(Medical　Sciences).　All　right　reserved.　Objective:　To　explore　the　protective　effect　of　the　antioxidant　N-acetylcysteine　(NAC)　on　the　retinal　nerve　tissue　of　early　diabetic　rats.　Methods:　We　randomly　divided　60　healthy　adult　Sprague-Dawley　(SD)　rats　weighing　between　180　g　and　220　g　into　2　groups:　normal　control　(CON,　n=20)　and　diabetic　(DM,　n=40).　By　intraperitoneal　injection　of　streptozotocin　(60　mg/kg),　the　model　of　diabetic　rats　was　established.　The　rats　were　considered　diabetic　only　when　they　had　hyperglycemia　(set　at　≥16.7　mmol/L)　(32).　The　CON　group　was　injected　with　the　same　amount　of　citric　acid　and　sodium　citrate　buffer　solution.　After　successful　model　establishment,　the　diabetic　rats　were　randomly　divided　into　1-month　diabetes　group　and　2-month　diabetes　group,　with　16　rats　in　each　group.　The　left　eye　of　each　experimental　diabetic　rat　was　set　for　diabetes　control　group　(D)　while　the　right　eye　was　set　as　NAC　treatment　group　(NAC).　At　2　weeks　of　diabetes,　4　μL　(1.6　μg/μL)　of　NAC　was　injected　into　the　vitreous　chamber　of　NAC　group　and　4　μL　(0.01　mmol/L)　of　PBS　was　injected　into　the　vitreous　chamber　of　the　other　diabetic　rats.　The　thickness　changes　of　outer　nuclear　layer　retina　was　observed　by　HE,　ultrastructural　changes　of　retinal　ganglion　cells　were　observed　under　the　transmission　electron　microscope,　and　the　number　of　retinal　ganglion　cells　was　detected　by　immunofluorescence　method.　Results:　At　different　time　points,　retina　outer　nuclear　layer　in　NAC　group　was　thicker　than　in　D　group　(P＜0.01).　However,　the　NAC　group　and　the　CON　group　did　not　differ　(P＞0.05).　Under　the　transmission　electron　microscope,　NAC　group　had　more　retinal　ganglion　cell　organelles,　higher　electron　density　of　the　cytoplasm,　and　milder　mitochondria　swelling　than　D　group.　The　NAC　group　did　not　differ　from　CON　group　in　the　ultrastructure　of　retinal　ganglion　cells.　NAC　group　had　an　increased　number　of　retinal　ganglion　cells　at　different　time　points　compared　with　the　D　group　(P＜0.01),　but　the　NAC　and　CON　groups　did　not　differ　in　the　number　of　retinal　ganglion　cells　(P＞0.05).　Conclusion:　The　antioxidant　N-acetylcysteine　has　a　protective　effect　on　the　retinal　nerve　tissue　of　early　diabetic　rats.