Understanding the impacts of climate change on agriculture production and the underlying mechanism in North China Plain is important to take effective adaptations for national food security. Using HybridMaize model, this paper investigated the impacts of climate change on summer maize yield potential and famers’ adaptation by changing varieties with longer growth periods from 1981 to 2010 in Xingtai County, Hebei Province. Results showed a significant warming trend with the average temperature increasing by 0.49 ℃·10 a^-1 since the 1980s. Both solar radiation and sunshine hours decreased significantly since the 1980s. The sunshine hours decreased by 0.56 h·d^-1·10 a^-1 and the solar radiation decreased by 265.1 MJ·m^-2·10 a^-1, while the precipitation kept constant with large variation among years since 1981. Yield potentials of both irrigated and rainfed maize were simulated to decrease by 0.63-0.64 Mg·hm^-2·10 a^-1 since 1981 if varieties were assumed fixed with the 1980s. This was mainly due to the decrease of solar radiation during the maize growth season and the shortened growth stage by warming, and around 60% of grain yield decrease was attributed to the decreased solar radiation. In practice, by changing varieties with longer growth periods, the growing degree days of varieties adopted by local farmers since the 2000s increased by 19% (280 ℃) compared to the 1980s, and consequently the yield potential was simulated to increase by 34%-40% (2.73-3.40 Mg·hm^-2) for both irrigated and rainfed maize.