[Objective] To reveal the differences in seismic performance between hardfill dams and concrete gravity dams， this study investigates the nonlinear seismic response of the Oyuk dam （a typical hardfill dam） in Turkey and the non-overflow section of the Xiangjiaba gravity dam in China. [Methods] Numerical models of the Oyuk dam and the non-overflow section of the Xiangjiaba gravity dam were built using the finite element method. We employed the Westergaard method to simulate the hydrodynamic pressure of reservoir， the concrete damage plastic model to represent the nonlinear material behavior of dam body， and the massless foundation model to avoid the motion amplification effect of the foundation. The seismic failure process and anti-sliding stability of the two types of dams were investigated under ground motions with different peak ground accelerations （PGAs）. The failure zones and controlling failure patterns of two dams were summarized. The seismic performance of two dams was compared using the failure indicator， cumulative plastic dissipation energy， and the anti-sliding stability safety factor. [Results] The failure zones of hardfill dam mainly occurred at dam heel， dam toe， and the upstream and downstream faces in the middle part of the dam. In contrast， the failure zones of gravity dam were mainly located at dam heel， locations of downstream slope change， and the upstream and downstream faces in the upper part of the dam. For hardfill dam， the controlling failure pattern was the penetration between failure zones on the upstream face and the downstream face， whereas for gravity dam， the failure pattern was the penetration from the downstream face to the upstream face. The symmetrical dam section of hardfill dam significantly enhanced its anti-sliding stability. The minimum anti-sliding stability safety factor of hardfill dam under the operating basis earthquake （0.24g） was 2.44， while that of gravity dam under design peak ground acceleration （0.222g） was 1.53. The anti-sliding stability safety factor of both dam types gradually decreased with increasing PGA. The safety factor for gravity dam decreased to 1.0 at PGA=0.5g， while that for hardfill dam remained at 1.17 at PGA=0.8g. Based on the failure indicator and the anti-sliding stability safety factor， the ultimate seismic capacity of gravity dam was determined at 0.45g-0.50g， whereas that of hardfill dam at 0.75g-0.80g. [Conclusion] This study reveals the differences in nonlinear seismic performance between hardfill dam and gravity dam. The ultimate seismic capacity of hardfill dam is significantly higher than that of gravity dam. In the construction of hydraulic engineering projects in high seismic regions， hardfill dam is an effective alternative dam type.