Interaction with virtual objects among different devices attracts lots of attention recently. LuminAR [Linder and Maes] was developed for a portable and compact projector-camera system for interactive displaying. THAW[Leigh et al.] was proposed to use a back-facing camera of a smartphone to assist the interactive displaying. RealSense [Lin et al.] was adopted the built-in compass sensor on a mobile device to calibrate the relative position among different mobile devices. However, the complex calibration process of LuminAR [Linder and Maes] and THAW [Leigh et al.] limited the applications. On the other hand, as addressed by the authors, once the users with mobile devices using RealSense [Lin et al.] move larger than 15 °, the positioning relationship cannot be kept stable. Therefore, in this paper, a 3D positioning scheme is proposed based on the built-in gyro sensor on a mobile device for effective and intuitive calibration and allow users to freely move the mobile devices with a natural user experience.