An installation damage test of geogrids and reinforced geosynthetics were performed at different installation depths (20, 30, 40, 60, 80 and 100 cm). A wide-width tensile test was used to evaluate both damaged and undamaged geosynthetics. The tensile strength of all geosynthetics decreased by 2~30%. The reduction factor was determined after evaluating the creep deformation behavior for 10,000 hours. The creep strain of damaged geosynthetics was approximately 1~2% higher than that of the undamaged geosynthetics under the same creep load conditions. These results may be used to predict the long-term performance of geosynthetics by estimating the reduction factor that accounts for construction-induced damage and creep deformation.