Three dimensional image fusion method and device are disclosed. The method includes steps of obtaining a spherical image and a two dimensional image; projecting the two dimensional image onto a planar surface predetermined in a spherical coordinate system where the spherical image is located, so as to acquire a projected image having a predetermined number of feature points on the spherical surface corresponding to the spherical image; determining multiple mapping points on the spherical surface which correspond to the predetermined number of feature points, letting the predetermined number of feature points superpose on the multiple mapping points, respectively, and carrying out spatial coordinate conversion, so as to attain a converted image; and mapping multiple points except the predetermined number of feature points in the converted image onto the spherical image based on a predetermined mapping relationship, so as to fuse the two dimensional image onto the spherical image.