Abstract: Five planting densities (4.50×10⁴, 5.25×10⁴, 6.00×10⁴, 6.75×10⁴ and 7.50×10⁴ plants·hm^-2, designated as T1, T2, T3, T4 and T5, respectively) were set up to explore the effects of planting density on canopy structure, dry matter accumulation and yield of summer maize, aiming to provide theoretical basis and technical support for highyield cultivation ofsummer maize in the hilly area of central Sichuan, China. The results showed that with the increase of planting density, leaf area index (LAI) of maize was significantly increased, whereas the stem diameter, the angle between stem and leaf, and the transmittance were significantlydecreased. With the planting density increasing by 1×10⁴ plants·hm^-2, the stem diameterdecreased by 1.4 mm in 2015 and 1.3 mm in 2016, the first leaf angles uppermost and underneath ear reduced by 3.601° and 1.440°, and the bottom transmission at silking and midfilling stages reduced by3.73% and 2.82%, respectively. The dry matter accumulation of individual maize was significantly decreased, while the dry matter increased with the increase of planting density. Compared with T1, the dry matter accumulation of per individual in T5 decreased by37.13% (2015),25.95% (2016) at the maturity stage, and the dry matter accumulation at communitylevel of 2016 increased by 26.72%, 23.41% in 7 days after silking and at the maturity stage, respectively. With the increase of planting density, the yield of summer maize firstincreased and then decreased, with the highest value being found at 6.00×10⁴ plants·hm^-2. At such a density, the group and individual function of maize reached a synergistic gain and maize yield compositions (effective panicle number, grains per spike and grain weight) were coordinated, which accounted for the increase of maize yield.

Key words: soil water, irrigation, fertilizer amount, electrical conductivity, yield