Nowadays, virtual reality (VR) technology has been widely used in various fields, but many VR systems will cause users to have an uncomfortable symptom when they bring immersive experience -- Virtual reality motion sickness. In order to understand the effects of virtual reality motion sickness on brain neural activity, this study recruited subjects to experience virtual reality motion sickness induced scenes by head-mounted VR, and recorded their EEG signals before and during the experience. Sample entropy and Power spectrum were used to extract EEG characteristics of subjects in different states, and significance test was carried out. In the whole frequency band, the mean values of Sample entropy at electrodes F8, F12, CZ, CPZ and OZ were significantly different, and the mean values of Power spectrum at electrodes F7, T7 and T8 were significantly different (P<0.01). In terms of frequency bands, the mean values of Sample entropy and Power spectrum in Delta and Theta bands were significantly different (P<0.01). The results show that the Sample entropy and Power spectrum analysis results may be related to virtual reality motion sickness, which is expected to be an effective index to measure virtual reality sickness.