Abstract: We studied the effect of different row spacing and density of corn on Radiation Interception (RI), Total Day Weight (TDW), Leaf Area Index (LAI), Next Assimilation Rate (NAR), Crop Growth Rate (CGR) and grain yield. The experiment was conducted in the field at research station of Isfahan, Iran on loamy clay to compare row spacing and to determine optimum plant density for maize hybrid K704. The experimental design was a randomized complete block in a split-plot arrangement with four replicates. Plot treatments were row spacing (60, 75 and 90 cm). Split-plot treatments were within-row spacing (12, 14, 16 and 18 cm). An increase of PP from 10.5 to 13.9 plants m2 increased LAI, TDW, CGR, RI and grain yield on average by 0.205 m, 48.4 g m1, 1.14 g m2 day1, 0.89% and 222.7 kg ha1 for each 1 plant per m2 added .but decreased NAR by 0.205 g m2 day1 for each 1 plant per m2 added. Moreover, when row spacing was reduced, RI, TDW, LAI, CGR and grain yield increased. But by reducing row spacing, NAR was decreased. The results show that the row spacing 60 cm, within-row spacing 12 cm and density 11.9 plant m2 for conditions of Isfahan is suitable for maize hybrid K704.