Aiming at the lack of reliability quantitative design method of the Exploding Foil Initiator （EFI）， the reliability design method for the Four-point Array output interface of EFI is studied. Firstly， based on the Stress-strength interference model， the reliability quantitative design method considering double margin coefficients is proposed， and the quantitative model between output performance parameters and reliability index is constructed. Then， the output performance of the output interface on different design parameters is simulated， and the quantitative models between the output performance parameters and structural design parameters is established. Finally， combined with the above two types of quantitative models， the structural parameters that meet the requirements of the output interface reliability design index of the four-point array slapper detonator are given. The results show that the method can effectively improve the reliability design accuracy of EFI’s output interface and then achieve accurate design.