The present experiment was conducted in the form of factorial based on  randomized complete blocks design with three replications with four levels of densities 8, 10, 12 and 14 plants per square meter and three hybrids of sunflower Sup.A, Sup.P and Sirat Isfahan agriculture research farm in 2013-14 cropping year. The results showed that the effect of plant density was significant on leaf area index, total dry matter, solar radiation absorption percentage in canopy, solar radiation depreciation coefficient and crop growth rate. The effect of cultivar was significant on total dry matter, solar radiation absorption percentage in canopy and crop growth rate. The interaction density and cultivar had no significant effect on all experimental traits. Increasing in plant density caused increasing leaf area index, total dry matter and crop growth rate. By increasing plant density from 8 to 14 plants per square meter, 95 percent light absorption was obtained which led to a significant increase in light extinction coefficient from 0.658 to 0.756 so that as a result total dry matter at the rate of 23.4 percent increased. Sup.A cultivar compared with other cultivars significantly allocated the most light absorption percentage (93.8 percent) and with the highest crop growth rate (24.9 gram per square meter per day) significantly produced the highest total dry matter (1672.3 gram). Thus, 12 plants density per square meter and Sup.A cultivar better used the advantages of the growth space for light absorption and dry matter production and might be suitable under the conditions similar to the present study.