Thickness analysis of tin coating on metal by Laser Ablation Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is affected by the laser pulse energy and its stability. A method has been proposed for quick measurement of thickness of tin coating on metal using a self-made picosecond laser ablation system coupled with Inductively Coupled Plasma Mass Spectrometry. Laser ablation was carried out using pulse energy of 12 μJ and defocus distance of 625 μm. Time resolved spectra (TRS) of ¹¹⁸Sn and measured isotopes of the main elements in substrate were acquired, the time of ablation of zinc coating was gained according to the relationship of these TRS, the ablation rate was calculated by thickness standard sheet, and thickness of tin coating could be measured quickly. Ablation rate of tin coating was 88 nm/pulse and depth solution was 0.40 μm. The thickness standard sheet and practical sample, including tinplate with paint coating and tinned stainless steel strip, were analyzed by this method. The maximum deviation between the found values and the certified values was 0.5 μm. This method avoids the instability of ablation rate which results in the change of ablation amounts of one pulse. This method improves the accuracy and is suitable for the thickness measurement of metal coating of different types, and could be used in fields such as life sciences, archaeology, environment, and judicial expertise.