The invention discloses an improved three-dimensional locating method of a wireless sensor network, and belongs to the technical field of wireless sensor locating. A locating area is continuously divided by using a VTM-APIT-3D algorithm, preliminary locating is performed by using a Fermat point model, a triangle centerline vertical plane is drawn to divide a locating space so as to shorten the locating range, meanwhile a triangle centerline or a line midpoint is further drawn by using a centerline (point) restoration method to divide the locating space, wherein processing is performed on four conditions according to different numbers of anchor nodes around an unknown node so as to realize three-dimensional locating of a wireless sensor, and accumulative errors resulting from that the unknown node is estimated within the effective range of a triangular pyramid shape for multiple times in the three-dimensional locating method adopting the Fermat point model are decreased.