Abstract: While moving along the lauching guide rail,a rocket sustains the action of dynanic loads resultin from the random uneveness of the rail,which is regarded as some definite function that can be applied to calculate the dynamic loads acting on the rocket.The paper gives a new way in such calculations. The spectral density function of the random uneveness of a launching guide can be deduced from the measured data.A quasi-random function in the form of a superposition of harmonic functions is introduced as the equivelent object function of the unevenes which is used to calculate the dynamic loads acting on the rocket.