Abstract: The durability, that is the service life of geosynthetics, is considered to be the primary problem when it will be chosen to use. The decay of mechanical performance is one of reliable indexes to evaluate the aging of geosynthetics. According to a series of tests and collected relevant test data, the theorefical model of mechanical durability of geosynthetics has been presented. The results obtained from the model show that if the initial tensile strength of geosynthetics is more than 500 N/5 cm with 40 cm thick covering soil, the service life of geosynthetics can be up to 50 years at least, and most can be over 100 years. It is concluded that the durability of geosynthetics is closely related to the natural environment temperature.