In this paper, the procedure of developing an unconstrained Genetic Algorithm code to solve mooring pattern optimization problems for floating structures is described. How to spread mooring lines around the offshore structures and tension level of these lines are the factors that have direct effect on response or offset of floating units which experience environmental conditions such as waves, wind and current. A GA may be used to search optimum mooring pattern and the best tension of lines to minimize floating structures offset. In this work, dynamic analysis is used to estimate floating units responses in a mooring optimization problem. Waves and wind are defined by appropriate spectra and analysis is performed in frequency domain. The goal for optimization is to minimize the objective function which is the sum of squares of the floating unit’s displacements for each set of environmental conditions. The considered variables of optimization are: position of anchors, line lengths and vessel heading relative to environmental conditions. Also size of mooring lines, and their material and strength are considered to be constant. It is assumed that all lines are from the same size and material and no buoy or counter weight is attached to the lines. To demonstrate the capability of the developed code, its application in a case study is presented and some conclusions are derived.