In order to investigate the effect of seed deterioration (accelerated aging test) on germination and seedling growth indices, an experiment was conducted. The accelerated aging test was carried out at three different temperatures (30, 40 and 50 °C) with four duration periods (24, 72, 120 and 144 hr) at 100% relative humidity on three cultivars of safflower (Soffeh, Arak2811 and PI) as a factorial experiment in completely randomized design with three replications in Agricultural Faculty of Yasouj University, in 2010. The results showed that accelerated seed aging or cultivar, temperature and duration period interactions have significant effects on germination percentage (GP) and rate (GR). Generally, by increasing temperature and time, characteristics of the seed germination and seedling growth of safflower such as length and weight of root and shoot and allometric coefficient decreased. According to the results, it seems, among the figures in long storage in hot and humid conditions, Arak-2811 had the most and Soffeh and PI, respectively, the lowest seed quality, including the percentage and rate of germination, root length and dry weight and seed vigor. Among the traits, shoot length, rootlet weight, allometric coefficient and seed vigor index were less affected by genotype and further reacted to deterioration. Consequently, it is advisable that in areas with lack proper facilities for seed storage (without temperature and humidity control) are lacking with more than 40°C for 72h and 100% relative humidity, it is better to use the Arak2811 variety with the ability to maintain the seed vigor and germination in this condition than Soffeh and PI.