The problem of evaluating reliability of telecommunication systems in general, and their components is considered. The method of forecasting the reliability of a telecommunications system designed according to the results of stress testing is proposed. The essence of the proposed method is to use the emissions of a random process as a diagnostic parameter that displays the trajectory of a monitored quantity values. As a quantitative measure of reliability used system average uptime. The simulation for normal distribution law of a random parameters with different correlation functions is carried out. The estimation of the average uptime for various sizes of tolerance range of parameters is calculated. It is shown that the theory of random processes emissions is an adequate mathematical apparatus for the formalization of the results of stress testing.