The satellites of Saturn, moving close enough to its rings or approaching them, cause noticeable gravitational perturbations. Simulation of perturbations from a satellite of the ring consisting of particles moving on almost circular orbits has been done. Methods of the N-body problem are used for investigation. The Saturn oblateness and a non-sphericity of disturbing satellite are taken into account. Equations of motion of the ring strands are modeled by chains of hundreds of particles while integrating. The ratios of a perturbation amplitude and offset from disturbing satellite depending on its mass and its distance to the ring have been found. The obtained results have been used to estimate the masses of Prometheus and Daphnis.