Thermal based laser surface cleaning could strongly depend on the temporal pulse shaping of laser. In this study, we have investigated, based on a Finite Element Method (FEM), the effects of different temporal pulses (Excimer laser, 248 nm, 26 ns), including rectangular and Gaussian shapes, in laser cleaning of microtapered slots covered by oil film (1.0 μm thick). The FEM model was verified with an analytical solution for a flat surface, and then applied to the tapered micro-slots structure. Plasma shielding effect as an important factor was included in current model. The temporal heating profiles with various laser fluences at different locations of micro-slot were obtained. Corresponding cleaning effects on the cross section of oil film were illustrated. Besides, a mesh size control equation was derived, which could ensure the modeling accuracy (<3% deviation). This work has laid down a theoretical base for further research work in laser cleaning of tapered micro-slots.