Hexaploid wheat (Triticum aestivum L.) exceeds about 30% of the world’s cereal production and cultivated over 220 million ha worldwide. Heat stress during the grain filling period gives detrimental effect on crop yields and has emerged as a serious problem throughout the world. Korean wheat cultivars that were released since 1960s were developed for various aims such as winter hardness, earliness, and pest resistance, etc. However, heat stress resistance is an emerging target for wheat breeding nowadays. Selected 11 Korean wheat cultivars (“Baegjoong”, “Dajung”, “Goso”, “Hanbaek”, “Jokyung”, “Joeun”, “Jopum”, “Keumgang”, “Olgeuru”, “Sinmichal”, “Uri”) were exposed to high temperature from DAF (days after flowering) 9~13. In this study, plant responses to heat stress as measured by reduction ratios of total chlorophyll contents, 100 seed weight, shoot dry weight can be translated into degree of tolerance. Therefore, these parameters can be used in wheat breeding for heat tolerance during grain filling period. The obtained results allow us to classify cultivars for heat stress tolerance. Pedigree information of Korean cultivars was shown that wheat line of either tolerant, moderate tolerant, or susceptible trait is succeeded to their descendent, which enable breeders to develop heat stress tolerant wheat by appropriate parental choice.