Abstract: Objective To evaluate the safety, tolerance and make sure the safe dose range of single dose and continuous Phenethyl Isothiocyanate capsules in Chinese healthy volunteers. Methods A single-center, double-blind, randomized, placebo-controlled trial was used. 12 healthy subjects were enrolled in a 28 days continuous drug-tolerance trial, with 6 subjects in the study and 6 in the placebo group. Oral Phenylethyl Isothiocyanate capsules, 30 mg/time, three times a day, continuous administration of 28 days. The clinical symptoms, vital signs, blood routine, urine routine, blood biochemistry, electrocardiogram and bladder ultrasonography were observed during the course of administration. The daily intake and withdrawal of the subjects were recorded and adverse events were observed and recorded. Results This study did not find drugs on male healthy subjects have a significant impact on the bladder. There were 12 adverse reactions, test drug group were 7, placebo group were 5. 3 subjects of the test drug group complained of dry mouth, while not in the placebo group. Conclusion The main adverse drug reaction is dry mouth. Taking into account the environment, continuous medication and the subjects themselves physiological changes and other factors, that 30 mg/time, TID is basically safe.