Abstract: A 360 video is stored as a 2D rectangle video through projection and packing.There are many projections and packing layouts,and their efficiency has a great influence on the resulting 360 video quality.In order to improve the quality and reduce the storage waste,we propose a projection algorithm using Peirce quincuncial and conformal mapping.The algorithm projects a hemisphere of the 360 video onto a disk by stereoscopic projection;then uses the Schwarz-Christoffel transformation to conformally map the disk to a square;so does another hemisphere.Then the two squares are stitched together continuously to obtain a 2D rectangle video.The experimental results show that our conformal projection algorithm can generate 360 videos with better continuity and smoother pixel distribution when compared to other commonly used algorithms.