AIM:To observe and research the expression of brain-derived neurotrophic factor(BDNF)in visual cortex of normal and monocular form deprivation amblyopia rats.METHODS:Model of monocular form deprivation amblyopia was established in SD rats by eyelid suture.Then the visual cortex was extracted and performed morphological analysis depending on Nissl’s dyeing,the expression of BDNF in visual cortex of P14,P21,P45,P120 MD rats was analyzed by immunohistochemistry SABC technique and computer graphics.RESULTS:Compared with the normal group,the number of neurons in visual cortex of MD rats was slightly reduced,neurons volume decreased,nuclear staining deepened.Expression of BDNF in normal visual cortex was consistent with visual development,P14-P21 the expression increased gradually,P21 reached peak,P45 decreased and P120 showed low expression,there was obvious statistical significance between P14 group and P21 group(P<0.01),and there was statistical significance between P45 group and P120 group(P<0.05);the BDNF kept low expression in visual cortex of MD amblyopia group,there was significant difference compared with the normal group(P<0.01).CONCLUSION:The expression of BDNF in visual cortex is consistent with the development of visual,it participates in formed synaptic styling in critical period of visual development,it is the molecular basis for amblyopia formation.