We developed a complex acceleration tester in order to identify the major stresses affecting the reliability of webbings. The major failure mode was defined as reduction in tensile strength. The accelerated test was performed for three different webbings with severer temperatures and UV irradiances than the real environmental conditions in order to confirm the effects of stress factors and save the testing time. The temperature, UV irradiance, and abrasion time were found to be the significant stresses affecting the failure of webbings. Results from the experiments using the acceleration tester may be used to establish the conditions for a practical small-scale laboratory accelerated test which could evaluate the reliability of webbings.