This paper presents the results of clinical observation and experimental research of Royal Made Ping An Dan (RPAD) of the Imperial Hospital of Qing Dynasty. The clinical results showed that RPAD was effective in treating 343 patients with motion sickness, and their average time for producing effect was 24.1 +/- 13.5 minutes. The total effective rates of dramamine group and Ren Dan group were 69.4% and 67.7% respectively, the latter included 45.7% of basically cured and 55.0% of markedly effective cases. There were significant differences among these groups (P < 0.05-0.01). It revealed that the effect of RPAD was better than that of dramamine and Ren Dan. According to laboratory findings, RPAD had the ability of alleviating symptoms of motion sickness and inhibiting eyeball tremor and improving meningeal microcirculation of experimental animals.