In order to study the interference characteristics between multiple wingsails on sail-assisted vessels during navigation, a lateral arrangement scheme of a two-element wingsail based on the relative wind direction angle was designed. The Reynolds averaged N-S equation was used for numerical simulation under steady conditions. The aerodynamic interference performance of the two-element wingsail was analyzed, and an optimization scheme for the angle of attack and flap deflection angle was proposed to address the stall problem caused by the interference of multi-sails. Furthermore, the interstage interference characteristics of wingsails were obtained. The results show that, in the single row arrangement scheme, the optimal spacing is 1.5c for relative wind angles of 30°, 90°, and 120°. However, the interstage interference can cause the wingsail to stall at the relative wind angles of 90° and 120°. After optimization, the auxiliary thrust coefficient can be increased by more than 5.2%, and the flow separation on the downstream wingsail disappears.