Abstract: The characteristics of some applied test-software were introduced when static and dynamic stiffness of products and components made of rubber or plastic were tested by using MTS810-100kN electric servo-hydraulic testing system. On the basis of the above stated, according to definite test conditions, measurement of static and dynamic of a series of vibration isolators used for rail were performed and influence of testing system deformation to measurement results were analyzed. The results manifested, it should be supposed to deduct the relative deformation of the testing system in the course of data processing.