Stiffness of flexible connectors has great impacts on responses of multi-modular floating systems but how to properly layout the anisotropic stiffness of connectors is unsettled yet. This paper presents a general approach to determine the stiffness configuration for various wave conditions. A genetic-algorithm-based routine procedure is thus proposed, which is capable to handle quite large number of influential factors in a decision making process. The linear weighted sum method is used for the preferences on individual objectives according to specific engineering requirements, tolerances and constraints. In numerical studies of eight-modular floating system, the optimal stiffness configuration is found in a full scenario of weight combinations. It indicates that the combination of small longitudinal stiffness, large transversal and large vertical stiffness is favorable for most wave conditions. This work makes the tedious task of the stiffness design be easy.