User posture can have an impact on cognition. Virtual reality (VR) devices extend the traditional two-dimensional interface into a three-dimensional space, necessitating some changes in body posture for users to interact between both. This study evaluated the interaction efficiency of standing versus sitting postures and the four corners of interface in VR environments. Thirty-five participants took part in the experiment, which measured the time they spent on searching and selecting targets under different conditions. With a two-way analysis of variance (ANOVA), the results indicated that the interaction efficiency of participants in a sitting posture was generally higher than that in a standing posture. When searching for targets on the left side, participants spent less time in both standing and sitting postures than on other areas. Specifically, searching for targets in the top-left corner took less time in a standing posture than other areas, while searching for targets in the bottom-left corner took less time in a sitting posture. The results suggested that posture also influenced cognitive performance in VR environments. Moreover, the high interaction efficiency could be achieved when the interface was placed at the top-left corner in a standing posture and at the bottom-left corner in a sitting posture. These findings could provide insights for VR developers on interaction design, enhancing optimal interface design according to different user postures to ensure expected interaction efficiency and user experience.