The invention discloses a thin-layer method for analyzing menthol crystal in cough-relieving decocted pear paste. The thin-layer method comprises the following steps: step 1: taking 20 g of the menthol crystal and adding 25 ml of petroleum ether; shaking and extracting for 1 h; taking supernatant and volatilizing until the volume is 1 ml, so as to obtain a test sample solution; step 2: taking a menthol crystal reference sample and adding absolute ethyl alcohol to prepare a solution which contains 2 mg of the menthol crystal in each 1 ml of the solution, so as to obtain a reference sample solution. The thin-layer method disclosed by the invention has the beneficial effects that the petroleum ether is used as an extracting solution, toluene-ethyl acetate is used as a developing agent, a 5 percent vanillin sulfuric acid-ethanol solution is used as a color developing agent and a silica gel G board is used as a display board, so that spots of color spectrum display of a menthol crystal thinlayer are clear, the repeatability is good and color developing deviation is eliminated.