The Method of Accelerated Testing of Reliability of a Mechanical System Elements treated by this work, contains significant advantages with respect to all other methods of reliability testing, that have been used so far in the engineering reliability testing practice in the world. The basic attributes of the method of accelerated multi-factorial testing of reliability of a mechanical system elements, described in this work, are: The function of the diagnostically parameter change in time is attained within the desired scope of the parameter; New plans for reliability testing in multi-factorial area (space); New statistical method based on regression analysis; Enormous decrease of the number of experiments and thereby of the costs of reliability testing in multi-factorial space, Interpretation of testing results is enabled in the form of Weibull distribution law in the whole defined multi-factorial space.