It is well-known that visually-induced motion sickness (VIMS) is caused by image motion. Therefore it is important to clarify the relationship between image motion and the change in discomfort level. However, it is difficult to know the quick change in the level of discomfort during watching actual video image. The authors have proposed a method of interpolation for the subjective score, which has low time and quantitative resolutions, by using physiological parameters. The model which represents the change in subjective score of VIMS was expressed as multiple regression equations in which input parameters are cardiovascular indices such as heart rate variability. In this study, the model which represents the relation between global motion vectors of a video image and estimated subjective score was identified as ARX model. The results indicated that the simple ARX model can estimate the change in subjective score from global motion vectors.