Oilseed crops have become the third most important crop in agriculture due to the production of essential food products, high nutritional values and reducing the risks of diseases. Among the oilseed plants, safflower ( Carthamous tinctorius L.) is considered as one of the sources of vegetable oil production in the world and in Iran. Although it has high culture potential in different climates, its cultivation area is limited. Obviously, the success of safflower cultivation and its development depends on breeding programs that lead to increasing yield and oil content in the different conditions. However, it seems that achieving this goal is not easy, because the genetic control of the traits, especially the traits associated with drought tolerance, yield and oil content are very complex and effected by environment. One of the most important breeding method is the QTL mapping which is the most effective one in plant breeding. A high genetic diverse population, suitable environment and selection based on the molecular markers are the most important features of this technique. Bulk Segregant Analysis (BSA) is a technique which reduces cost and time and leads to identify more markers related to interested trait. In previous studies using generation derived from the interspecific hybridization between C . oxyachantus and C . tinctorius , a high correlation was observed between capitulum diameter and yield. By testing it on the upper and lower bulked thresholds, a SSR marker associated with this trait was identified, which would confirmed by repeating tests on threshold individuals. By testing this marker on bulks and individuals of upper and lower threshold, it showed that this marker could not be a reliable marker for the capitulum diameter and the correlation between this trait and the marker, did not confirmed through these experiments. Also, with further experiments using SRAP and SCoT markers, there was no consistent indication. According to the results, this indicator relationship requires further examinations. By increasing the number of testing population, quantity and quality of the DNA samples and using more markers or other marker systems and using multiple markers simultaneously could help to identify markers correlated with this trait. Key words: Safflower, Capitulum diameter, Quantitative Trait Loci, Bulk Segregant Analysis