To obtain an optimum connection parameter combination of multiple functions for modular floating structures, an integrated methodology for the assessment and optimization is proposed in the present work, out of consideration for the balance between the functional performance and economic effect. To illustrate the whole process, two types of modular floating structures, i.e. a modular wave energy converter (WEC) and a modular mobile offshore base (MOB) are taken as the cases. For the two cases, connection configurations are firstly specified based on structural functions as well as environment conditions; then quantified measurements are established and studied, based on which the following process of selection of optimization algorithms is done and the optimum solutions are obtained, making up a whole process of specification of the connection parameter combination for modular floating structures. The proposed methodology possesses the potential of offering guidance for the phase of preliminary design of connection structures of modular floating structures.