Abstract: A reagent, test paper, a reagent kit, and a test paper kit for detecting a sulfhydryl compound, and a preparation method thereof are provided. The reagent is obtained by mixing a phosphotungstic acid (PTA) reagent, an acetate buffer, and a shield reagent in a specified ratio. The test paper is composed of porous water-absorbent paper and a dry detection reagent dispersed thereon. The reagent is based on principle innovation. When in use, the reagent is directly mixed with urine to be tested in a volume ratio of 2:1, a resulting mixture is allowed to stand for 10 min to 15 min, and then a result can be directly determined by naked eyes. The reagent overcomes the shortcoming of requiring a control sample to assist in the determination of a result in existing methods, and has the advantages of simple operation, safety and non-toxicity, and rapid detection.