Frequent extreme climate events such as droughts and high temperatures caused by global warming have led to a 32%-53% decrease in the emergence rate of direct-seeded rice compared with the baseline level, seriously threatening food security. Hydropriming, as a low-cost seed pretreatment technology without chemical residues, can enhance germination efficiency and stress resistance by regulating seed metabolism and gene expression. In this study, four different rice varieties, namely Wuyoudao 4, Yuxiangyou 8133, Yongyou 4949, and Yuxiangnuo 1, were used as materials. Combined with the determination of seed coat thickness, the seed germination process and physiological responses under hydropriming (T treatment, hydropriming treatment) and non-priming (CK, control treatment) were analyzed to explore the effect of seed coat thickness on priming efficacy. The results showed that there were differences in seed coat thickness among the four varieties, which were closely correlated with germination and resistance indices after priming. The T treatment significantly advanced the initiation time of germination by 1-2 days, and the germination index was significantly increased. For example, the germination indices of Wuyoudao 4 and Yongyou 4949 increased by 42.87% and 24.03%, respectively. However, the germination energy and mean germination time decreased, and there was no significant difference in the final germination rate between the T treatment and CK. In terms of resistance, the T treatment reduced the malondialdehyde (MDA) content and increased the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) of all varieties. For instance, the POD activity of Wuyoudao 4 in the T treatment was 65.52% significant higher than that in CK. Yuxiangnuo 1, with a thicker seed coat, showed an 22.39% increase in root length under the T treatment compared to CK. Its biomass and root-shoot ratio, and SOD activity increased singnificantly, with its biomass and root-shoot ratio being the highest among the four cultivars. In contrast, Yongyou 4949, with a thinner seed coat, exhibited the lowest germination energy and the largest decrease in MDA content(43.62%). The study indicated that seed coat thickness affects the germination response and resistance performance of rice seeds to hydropriming by regulating water absorption and the antioxidant system, providing a theoretical basis for drought-tolerant variety screening and optimization of direct-seeding techniques.