The past researches on the transient responses of rotor-bearing systems under shock excitations paid little attention on impact-contact-rub forces which would arise when taking journal- bearing clearance into account, and these forces’ influences on the overall responses remain unknown until now. In this paper, models of impact-contact force, rub force and oil-film force in a rotor-bearing system were built respectively. Numerical calculation was performed to obtain time-varying responses of those forces while the system suffers base-transferred shock excitations. Influences of those forces on system overall responses were investigated. The main conclusion is that the rub force has no obvious influence on the system responses during shock lasting time, whereas it shows an obvious inhibitory effect on the residual response, making time-varying amplitudes be smoother. Rub force maybe bigger in x direction than in y direction although shock energy in x direction is less than in the y direction. Influences of the oil-film force on response is similar to that of rub force but more severely. It has obvious influences on overall responses both during shock lasting time and residual time.