Abstract: Leaf free space plays an important role in nutrient exchange between environment and plant canopy, and is a major field of plant nutritional research. A pot experiment was carried out with different plant types of maize to study the differences of leaf apparent free space (AFS) at different layers of canopy under different nitrogen (N) fertilization treatments. The plant types of summer maize were plate conformation Shandan 9, middle conformation Nongda 108 and compact conformation Shandan 902. The N rates were N 0, 0.15 and 0.30 g/kg. The results showed that AFS of canopy leaf was significantly different at different growth stages, and decreased gradually with growth, as well as the biomass and total N content. The interaction between variety and N rates was significant for AFS, biomass and total nitrogen content across the whole growing period, except the interaction for AFS at maturity stage. There was not a significant effect of N fertilization on biomass, but total leaf N content increased significantly with N rate. AFS of canopy leaf was significantly different among different N rates, with AFS of mid-level N fertilization treatment being larger than either no or higher N fertilization treatment. Leaf AFS, biomass and total N content differed with different layers of plant canopy, N fertilization rates and varieties across different growth stages. Among different maize plant type, AFS of compact middle conformation Nongda 108 and plate conformation Shandan 9, and the average were 9.06% and 8.85%, respectively. Correlation analysis showed that there was a significantly positive correlation between total N content and AFS. The research indicated that AFS of canopy leaf was not only controlled by genetic characteristics of plant, but also affected by nutrition of plant and medium. AFS was significantly affected by the nutrient levels of plant and medium and growth stages.