Objective To explore the improving effects of motion sickness acclimatization training methods, namely sinusoidal vertical oscillation stimulation and sinusoidal vertical oscillation stimulation combined with visual virtual reality (VR) swell stimulation, on cognitive performance of individuals with extremely severe motion sickness. Methods A total of 90 individuals with extremely severe motion sickness screened by the Graybiel score during 6 h navigation were randomly divided into vertical group, vertical＋VR group, and control group (n＝30). The abilities of vigilance, memory, rapid calculation, information processing and visual manipulation were evaluated before and after the acclimatization training using a self-developed cognitive performance evaluation software. Results On the 1st day of training, the numbers of missed targets of the vertical group and vertical＋VR group were increased in the vigilance test; the reaction time was prolonged in the short-term memory, rapid calculation, information processing and visual manipulation tasks; and the efficiency of rapid calculation was reduced. After acclimatization training, the numbers of missed targets were reduced to the baseline level in the vertical and vertical＋VR groups, and the reaction time in the short-term memory, rapid calculation, information processing and visual manipulation tasks and the efficiency of rapid calculation were improved. Conclusion Motion sickness caused by vertical oscillation stimulation or vertical oscillation combined with visual VR swell stimulation can decrease vigilance, short-term memory, rapid calculation, information processing and visual manipulation abilities. Motion sickness acclimatization training can significantly improve the above cognitive abilities.