Floating storage system has been recently proposed as a new method for stockpiling emergency petroleum reserves. In this system, floating storage barges are moored to mooring and loading dolphins by way of rubber fender. For mooring design of these barges, analysis is essential for the behavior of the barge in connection with mooring facilities having non-linear resilient characteristics. In this paper, non-linear mathematical model of moored floating storage barge is investigated by various basic approaches and some results of numerical simulations are introduced. Results of these investigations show as follows : (1) Numerical simulation by non-linear mathematical model is available for mooring design of a floating barge. (2) Adopted fender is effective for energy absorption without excessive fender reaction forces.