Abstract: The aim is to determine the relationships between planting density and yield, component factors of yield and population physiological indices of sorghum. The extremely early-maturity hybrid‘Tongzao No. 2’ was used as the material in a field experiment. The randomized block design was adopted with three repeats. 5 planting densities (150-thousand, 180-thousand, 210-thousand, 240-thousand, 270-thousand plants/hm2) were employed. The results showed that, the plant height of sorghum was increased and the stem diameter became thinner along with the increasing planting density, but the dry matter weight per plant, population net assimilation rate, population growth rate were significantly decreased as planting density increased. The leaf area index, leaf area duration and the total leaf area duration were significant increased with the increasing planting density. When the planting density was at the range of 150-thousand to 210-thousand plants/hm2, the grain yield significantly increased with the increasing planting density. Along with the increasing planting density, the grain yield showed a downward trend, and there was significant difference of grain yield among the treatments. Panicle number per unit area increased with the increasing planting density, but the grain weight per plant and 1000-grain weight decreased with the increasing planting density, and the difference among treatments was significant. It is concluded that, when the planting density is 210-thousand plants/hm2, the spacing is 9.5 cm× 60 cm, the sorghum hybrid‘Tongzao No. 2’could coordinate the population structure well and obtain higher grain yield.