Incomplete optical distortion correction in VR HMDs leads to spatial dynamic distortion, which is a potential cause of VIMS. A perception experiment is designed for the investigation with three spatial distortion levels, with the subjective SSQ, five-scale VIMS level rating, and objective postural instability adopted as the evaluation metrics. The results show that the factor of spatial distortion level has a significant effect on all metrics increments (p<0.05). As the spatial distortion level drops off, the increments of VIMS symptoms decrease. The study highlights the importance of perfect spatial distortion correction in VR HMDs for eliminating the potential VIMS aggravation effect.