Objectives; Korea Hydrographic and Oceanographic Agency (KHOA) developed Korean motion sickness index which estimates the incidence of sea sickness and helps prevention of sea sickness for citizens and ship crew. Because avoidance of sea sickness is impossible for naval crew, prevention and supply of anti-sea medication is important in sailing. Method and material; This research was an ecologic study in two naval destroyers. The study included available sailing days which includes domestic sail records from April 2018 to October 2018. We collected daily Korean motion sickness index from KHOA and daily supply of anti-motion sickness medication. Motion sickness index was divided into 5 stages (Very good, good, usual, bad, very bad). We defined anti-motion sickness medication consumption rate (AMCR) as (total consumption of anti-motion sickness medication) / (total crew numbers) X 100. Motion sickness index and AMCR were compared with univariate analysis. Results; Among available 60 sailing days, motion sickness index of "good" was 15 days, "usual" was 31, and "bad" was 14 days. There was no "very good" or "very bad" days among sailing days. Average scores of components in motion sickness index were 3.32 for wave height, 4.42 for ship weight, 1.55 for sailing time, and 2.72 for maximum wind speed. Averagic AMCR were 2.44%. AMCR for "good" sailing day was 0.22%, "usual" was 1.36%, and "bad" was 6.99%. The medication consumption was increased in "bad" sailing day by 31 times. Conclusions; We found inverse correlation between motion sickness index and AMCR in this study. Before sailing, supply of motion sickness medication could be estimated through Korean motion sickness index.