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The concept of the close-encounter probability was applied to simulate the angle-dependent surface peak intensities in coaxial impact collision ion scattering spectroscopy (CAICISS). It needs to follow incident trajectories only from a top surface up to several tens of monolayers below a surface and reduces the computing time remarkably. The simulation was performed for a polar-scan spectrum for TiO2-terminated SrTiO3(001) using 3 keV He+ beams incident upon its (100) plane. This method reproduced well the observed polar-scan spectrum for Sr peak intensities except for grazing incidence less than 30°. On the other hand, the Williams' method, which has been frequently utilized, gave pronounced deviation due to neglect of the contributions from the depths. The applicability and limitation of the present method is discussed in detail.