Objective To study the acclimatization time and effects for preventing motion sickness under sinusoidal vertical oscillation stimulation,visual virtual reality(VR)swell stimulation,and their combined stimulation.Methods Totally 120 individuals with extremely severe motion sickness during 6 h navigation were randomly divided into 4 groups(n=30):vertical group,VR group,vertical+VR group,and control group.The severity of symptoms during the training period was assessed daily by Graybiel scale,and the number of drops from flexible treadmill in the VR group was recorded.The Graybiel score of 0 for 3 d and/or the number of drops for 0 were considered as complete acclimatization.The training effect was validated by navigation under more severe sea conditions.Results The Graybiel scores of the vertical group and vertical+VR group,as well as the number of drops of the VR group were decreased with the increase of training days,and reached the acclimatization level on the 3rd,5th,and 2nd training day,respectively.The longest acclimatization time in the vertical,vertical+VR,and VR groups was 8,8,and 5 d,with an average acclimatization time of 3.6,3.9,and 2.7 d,respectively;the acclimatization rates within 5 d were 93.33％(28/30),76.67％(23/30),and 100.00％(30/30),respectively;the proportions of individuals with effective acclimatization training in the verification voyage were 86.67％(26/30),96.67％(29/30),and 66.67％(20/30),respectively;and the training efficiency was 85.19％,96.30％,and 62.97％,respectively.Conclusion Three training methods all have effects on motion sickness acclimatization,and the acclimatization period is 5-8 d.The acclimatization effects of the vertical oscillation and vertical oscillation+VR training are better than the VR training.