This paper aims to study the impact of the Copulas function for modeling the dependence structure between shear strength parameters on geotechnical system reliability and reveal how the dependence structure of shear strength parameters affects the system reliability. The method for modeling the dependence structure of shear strength parameters with incomplete probability information is first introduced. Then the Monte Carlo-based simulation is performed to analyze the system reliability by taking into account Copula-based bivariate distributions of shear strength parameters. Finally typical geotechnical structures such as a retaining wall and a rock wedge slope are analyzed to demonstrate the impact of Copula selection on geotechnical system reliability. The results indicate that the Copulas function provides an effective way to construct the bivariate distribution of shear strength parameters. The difference of geotechnical system probabilities of failure among various Copulas is significant and should not be ignored. In addition, the impact of Copula-based dependence structure on geotechnical system reliability consists of two processes essentially: one is the impact of dependence structure between shear strength parameters on the probability of each failure mode and the other is the impact of all failure modes on system reliability.