Abstract: Nitric oxide(NO) plays an important role in growth and development of plants.In this study,we used Sodium Nitroprusside(SNP) as NO donor to examine the positive effect of NO on photosynthetic structure and its activity in iron-deficient maize grown in nutrient solution for 20 days.The results showed that NO could completely reverse the inter-veinal chlorosis induced by iron deficiency and increase chlorophyll content in the leaves of maize seedlings.Electro microscope analysis showed that NO promoted the chloroplast development,as indicated by increased number and size of chloroplast in both the mesophyll cell and bundle sheath cell of the leaves,and well-developed stroma lamellae and grana as well as increased numbers.Further studies showed that the assembly of protein complexes of thylakoid membranes was significantly promoted and the electron transfer rates in thylakoids were enhanced by NO treatment,so the photosynthetic activity of leaves was obviously increased.