Abstract: The dynamic accumulation and thermostability of Hydroxy Safflor Yellow A (HSYA) were studied in order to provide certain theoretical basis for production and application of Carthamus tinctorius. Carthamus tinctorius‘Yanjin’and Carthamus tinctorius‘Yuanyang’were taken as the study materials, HSYA content at different development stages, and HSYA content of safflower filaments in different temperatures and time were analyzed using high performance liquid chromatography method. The results showed that HSYA began to accumulate in the forming period of buds, and reached a peak on the third day after flowering. The HSYA content of standard substance decreased in a straight line with the storage temperature (50-100℃) increase within the same storage time, and it also showed a sharp decrease with the time increase (30-120 min) in the same temperature environment. HSYA content of safflower filaments continuously increased during 30-240 minutes at 50℃, and peaked at 240 min. HSYA content peaked at 90 min under 70℃, then began to decrease when the time was more than 90 min. The HSYA content decreased rapidly during 100-140℃, and declined sharply with the time increase (30- 240 min) in the same temperature environment. So the best picking time of safflower was the third day after flowering. Safflower filaments were dried at 40-50℃, and safflower preparation should avoid high temperature condensed method.