Abstract: To provide theoretical basis for the selection of planting materials and cultivation techniques of bitter gourd in summer in Hainan province, the differences in heat tolerance of different inbred lines of bitter gourd at the germination stage were evaluated. Three inbred lines of KG 10-1, KG 14-4 and KG 18-2 used as test materials, three temperatures of 30 ℃,33 ℃ and 36 ℃ were set, and the sand bed method was used for germination. Principal component analysis was performed on the rate of change of 10 germination indicators such as germination rate, seedling rate axial length, root length, fresh weight, and dry weight. The results showed that with the increase of temperature, the seed germination and seedling formation of the three bitter gourd inbred lines were inhibited. When the germination temperature reached 36 ℃, the average germination time significantly prolonged, and the germination rate, germination rate index and germination index significantly decreased. Three inbred lines failed to grow into seedlings. The order of heat resistance performance of the three bitter melon inbred lines at 33℃ from strong to weak was KG 18-2, KG 14-4, KG 10-1 according to comprehensive score value of the principal components analysis. Therefore, in summer cultivation, seedlings could be raised at a temperature of about 33 ℃, and the KG 18-2 inbred line with better heat resistance should be recommended.