Abstract: In the evaluation of structural performance and service behavior of gravity dams, the traditional probabilistic reliability analysis method is restricted by many factors, such as strict randomness of uncertain parameters, oversensitivity of calculated results and high nonlinearity of function function. A non-probabilistic reliability (NR) analysis method for gravity dam elements and system based on the interval parameters is proposed. First, according to the prototype monitoring data and the achievements of physical and mathematical models for gravity dams, the interval parameter boundary of the gravity dam is obtained. A NR model based on the interval parameters is established, and a method for calculating NR index (NR-η) based on response surface method is developed by using the interval mathematics and NR theory. Then, the safety of the gravity dam system in single and multiple failure modes is analyzed from the possible failure paths and modes. Finally, based on a gravity dam, the results indicate that the proposed method can effectively reveal the local and overall reliable states of the gravity dam. The calculated results are in good agreement with the background conditions of the dam under the premise of the operating characteristics of the gravity dam.