Node deployment is one of important questions in three-dimensional wireless sensor networks(3D WSNs) for the mountain monitoring. In this article, sampling coverage is proposed,and node deployment with sampling coverage is abstracted to mathematical spacing-filling study. The solving method is verified in two-dimensional wireless sensor networks(2D WSNs) firstly,then it is extended to 3D WSNs.Several space-filling polyhedrons are used to fill three-dimensional solid space,and volume entropy is defined to evaluate space-filling perfermance. We can use the minimum nodes to constructe 3D WSNs if choose the vertexes of truncated octahedron to set nodes. That deployment method can both achieve seamless sampling coverage and high connectivity based on computer simulation.