8 kinds of woven and nonwoven geotextiles with design strength were used for plasma treatment. To perform hydrophobic treatment of woven and nonwoven geotextiles, C2F6 gas was used under electric power of 500 watt, plasma treated time of 10 and 20 min, and gas flow rate of 1500 sccm on treatment condition. For hydrophilic treatment of geotextile composites, O2 gas was used in the condition under electric power of 2500 watt, plasma treated time of 10 and 20 min, and gas flow rate of 2000 sccm. As result of plasma treatment, tensile strength of geotextiles increased after plasma treatment, but chemical resistance had not altered. For examining the engineering performance of geotextiles in sea water, 3.5% NaCl solution as artificial seawater was applied and the long-term strength retention and reduction factor was determined from strength retention. Finally, Arrhenius plot is applied to evaluate sustainable applicability of PET spunbonded nonwoven geotextiles at 25�Ž is predicted. Keywords: Nonwoven Geotextiles, Plasma Treatment, Hydrophobic and Hydrophilic Treatment, Artificial Seawater, Long-Term Performance, Arrhenius plot.