[en] In our previous experiment on CR-39 detectors, we found out that bulk etch rate of irradiated area is different from unirradiated area. Therefore, the traditional etching model should be revised. In this case, our modification which based on the theoretical studies printing out and the AFM observation was put forward and new etch rate : V'=V_t/V_irr, was defined. Then, modified track-diameter kinetics was used to clarify AFM analysis. In this research, the key parameters for 100 MeV Silicon ion include V_t=4.12 μm/h, V_irr=2.55 μm/h, V'=1.62, θ=61.03°. And the bulk etch rate V_b=1.58 μm/h. So the etch rate can be calculated whose value in V=2.61>V’. (authors)