China's hydropower resources mainly concentrated in west China, which is also the meizoseismal area of China. The seismic safety of high earth rockfill dams in these areas is one of the most serious problems in China's hydropower development. Based on the relevant provisions of Code for seismic design of hydraulic structures of hydropower project (NB 35047—2015), the three-dimensional nonlinear seismic response analysis of Lianghekou super high core rockfill dam was carried out by using the ground motion time history generated by site related design response spectrum of the scenario earthquake. The research results show that the dam acceleration amplification effect was quite significant in the middle part of the valley which is exactly of 4/5 dam height above and within 1/3 dam axis length for Lianghekou super high core rockfill dam located in a V-shaped Valley. It showed obvious whiplash effect and three-dimensional valley effect. On this basis, the reinforcement range of Lianghekou super high core rockfill dam was proposed.