Evaluating plant stress tolerance and screening key regulatory genes under the combined stresses of high temperature and drought are important for studying plant stress tolerance mechanisms. In this study, the drought tolerance of five grape varieties was evaluated under high-temperature conditions to screen key genes for further exploration of resistance mechanisms. By comparing and analysing the morphological characteristics and physiological indicators associated with the response of grapevines to drought stress and integrating them with the membership function to assess the strength of their drought tolerance, the order of drought tolerance was found to be as follows: 420A>110R>Cabernet Sauvignon (CS)>Fercal>188-08. To further analyse the mechanism of differences in drought tolerance, transcriptomic sequencing was performed on the drought-tolerant cultivar 420A, the drought-sensitive cultivar 188-08 and the control cultivar CS. The functional analysis of differential metabolic pathways indicated that the differentially expressed genes were enriched mainly in biological process category, that 420A had higher antioxidant activity. Furthermore, differentially expressed transcription factors were analyzed in five grape varieties. Genes like VvAGL15, VvLBD41, and VvMYB86 showed close associations with drought tolerance, indicating their potential role in regulating drought tolerance and research significance.