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In Indonesia, one of the regions that has good potential for Floating Offshore Wind Turbine (FOWT) installations is the Natuna Sea which has a fairly good average wind speed in the range of 7.0 - 11.0 m/s. In addition, the Natuna Sea has water depth of around 80-250 m with relatively mild wave height. This condition is a suitable environment for the installation of the FOWT. Therefore, it is necessary to investigate the appropriate mooring system configuration due to the motion of the structure. This paper examined the analysis of mooring system of the SPAR type FOWT structure due to its global motion through numerical modeling by using open source software FAST. The Spar structure was successful applied in the offshore oil and gas industries which has a special feature of deep-draft so that its motion characteristics are very good/stable because the Spar is not too affected by wind, waves or ocean currents, compared to other floating structure types. The Spar use is even capable of up to a depth of 10,000 ft (= 3,048 m). The analysis was carried out for operation condition, by varying three configurations of the mooring system for direction of environmental loads (waves and winds), namely 0 degree (perpendicular in front of the turbine), 45 degrees, and 90 degrees (the turbine side direction) and wind speed. With the scope of such analysis, it could be properly examined the mooring system due to global motion of heave, roll and pitch of the Spar. This situation will prevent the Spar to structurally collapse and in turn its motion will not decrease the efficiency of the wind turbine itself.