A high-power continuous-wave laser is applied in this study as a replaceable surface treatment method for steel structures. Various forms of corrosion pits will affect the laser treatment efficiency for surface preparation of severely corroded steel structures. In order to evaluate the effect of laser treatment on the steel surface with corrosion pits, carbon steels with artificial pits of various depths and widths were performed and treated by laser irradiation. SEM-EDX analysis distinctly identified laser-treated areas under conditions by mapping elements. Results indicate the laser beam can reach the bottom of pits, promising cleaning efficiency of laser irradiation is still worth expecting.