Climate change makes the Earth warm day by day is one of the most serious risk threatens rice production in the future. This research used 02 SSR markers RM3586 and RM3735 to evaluate heat tolerance genotypes of 53 rice lines/varieties imported from IRRI and genetic resources of the Cuulong Delta Rice Research Institute. The heat tolerance lines/varieties were then continued phenotypic screening to select promising rice varieties for development into the large scale production. Results of genotypic analysis used RM3586 marker identified 35/53lines/varieties with heat tolerance genotypes. Polymorphism of PCR products were not found in all varieties by RM3735 marker. They gave the same size of 170bp for all DNA samples. Results of 35 lines/varieties phenotypic screening for heat tolerance traits in comparison with OM5451 check variety, identified 02 rice varieties with strong heat tolerance (scored 1) were OM124 and OM300; 15 moderate heat tolernce rice varieties were defined (scored 3) included: DV108, OM380, OM9584, OM225, OM221, DTS4, DTS19, OM22, OM9582, OM7167, OM121, OM108, OM178, OM189, DTS9. These rice varieties were being tested in Dong Thap to select the promising rice varieties added to the variety structure of the province.