The invention discloses a preparation method of a test paper for fast detecting heavy metal cadmium in tobacco leaves. The preparation method comprises selecting a medium-speed quantitative filter paper, preparing a cadmium reagent solution having a mass fraction of 0.2%, fully soaking the filter paper into the cadmium reagent solution, taking out the filter paper after full infiltration, and carrying out airing to obtain the test paper after the solvent is fully volatile. The cadmium reagent capable of producing a special-effect chromogenic reaction is loaded to the test paper through immersion so that the heavy metal cadmium fast test paper is prepared. The system optimizes various factors for influencing test paper strip preparation and detection and ensures the optimal test paper preparation and detection conditions. The inductively coupled plasma mass spectrometry (ICP-MS) verifies the effectiveness of the test paper strip. The test paper strip can be successfully used for fast, real-time and on-site detection and screening of cadmium (Cd<2+>) in a tobacco leaf sample and has the detection limit of 0.5 microgram per milliliter.