Abstract: It is generally believed that the requirement of hybrid rice seed production system to environmental conditions is stricter than that of common rice plant production under the field conditions, but the conclusive evidence has been lacking. In 2013, a rarely continuous hot weather had affected Yangtze River valley, and the high temperature days maintained until the rice anthesis stage. The impact caused by this abnormal heat wave on the pollination of pollens of male parents to the stigma of the female parents acted as a great chance to ob?serve the susceptibility of the seed production system to high temperature. The experiment was conducted at the biggest hybrid rice seed production base which located in Yancheng City, Jiangsu Province, China. Three batches of seeds including male and female parents with specific interval sowing dates were planted in the field to produce hybrid seeds F1. For different batches’plants flowered at different dates, they thus experienced var?ied temperature at their developmental stages. We took the seeding batches as the experimental treatments, which were planted in an interval contrast design with three replications in the field. As a result, the male par?ents for three batches all had moderate decreases in seed setting rates, but a sharp decrease was observed for all three batches female parents as contrasted to that at normal temperature year (30%-40% down, in absolute value). There has been no difference among the seed setting rates between the three batches of male parents. Meanwhile the seed setting rates between three batches of female parents showed significant difference, the seed setting rate of the female parents was significantly correlated with the high-temperature days they experi?enced. Those results showed that high temperature might affect hybrid rice seed production much greater than the normal rice production. Selecting hybrid rice parents with more tolerance to heat stress and developing countermeasures would be the focus of hybrid rice research.