<p>In order to study of plant density effect on silage yield of new maize hybrids an experiment was conducted in factorial on the basis of randomized completely block design with four replications at agricultural research station in Qarakheil (Qaemshahr) in 2014 in Iran, after wheat harvesting. New hybrids are SC703 and SC705 that were compared with SC704. Four densities were 75,000, 85,000, 95,000 and 105,000 plant per hectar. Eeach plant planted in four rows with intera-row spacing of 75 cm. Silage yield, plant height, ear height, kernel number in ear row, kernel row number,dry silage yield, kernel, stem and leaves protein were measured. Result showed that SC704 had the highest silage yield with 70.96 t/ha. SC705 and SC703 had 64.67 and 60.22 t/ha silage yield. Density of 105,000 and 95,000 plant per hectar had higher silage yields in compare of other densities with 67.04 and 66.20 t/ha respectively. Result showed that SC704 had the highest dry silage yield with 43.19 t/ha. SC705 and SC703 had 38.69 and 36.75 t/ha dry silage yield respectively. Density of 105,000 and 95,000 plant per hectar had higher dry silage yields in compare of other densities with 40.67 and 40.55 t/ha respectively. With increasing of density, crude protein (in kernel, stem and leaves) decreased.</p>