The invention provides a preparation method of a tinned steel plate with ultralow tin content and application of the preparation method. The preparation method comprises the following step that a steel plate is subjected to cleaning, electrotinning, soft melting and passivation to form the finished tinned steel plate, specifically, the roughness of the steel plate is 0.2-0.40 microns, the electroplating current density in the electrotinning process is 8-15 A/dm<2>, the concentration of an electroplating solution Sn2+ is 12-20 g/L, a pure sensing soft melting technology is adopted in the soft melting process, the soft melting temperature is 250-260 DEG C, and the soft melting height is 4000-4500 mm, and in the passivation process, a sodium dichromate solution with the concentration being 20-30 g/L is adopted as a passivation solution. By adjusting the electrotinning process, the soft melting process and the passivation process, the tinned steel plate with a thinner coating is obtained,the surface tin content of the tinned steel plate is 0.60-1.00 g/m<2>, the pure tin content is 0.20-0.60 g/m<2>, and the film adhesion is lower than or equal to grade two.