Levo Phencynonate Hydrochloride for the Prevention of Seasickness

Inclusion Criteria: * Subjects fulfilling the diagnostic criteria for motion sickness * Have medical history for motion sickness * During screening, the severity of sea sickness is assessed as moderate or above according to sea sickness severity scale. * Adults for 18-55 years, male or female. * Agree to participate the study and can sign the ICF independently. Exclusion Criteria: * Be allergic to the study drug or be allergic constitution * ALT, AST≥ 1.5 times of ULN, Scr\>ULN, or other clinical significant lab values. * Abnormal ECG which is clinical significant judged by investigators, including: QTc\>normal range * Have medical history for urination disorder * Have headache, vertigo, dizziness or nsomnia caused by other diseases than motion sickness. * Have active gastrointestinal diseases or overweight (BMI≥24kg/m2 ) * Have internal ear disease which may disturb the evaluation of motion sickness. * Have glaucoma or posterior circulation ischemia * Have anxiety, depression or other mental disease that investigator considering inadaptable to participate the study. * Participated in other studies within the past 3 months.