For the problem of coverage in 3D Wireless Sensor Network (WSN), this paper introduced a Three-Dimensional Coverage Algorithm based on Adjustable Radius in wireless sensor network (3D-CAAR). Virtual force was used to achieve uniform distribution of nodes in WSN, at the same time, the distance between a sensor node and the target points in the covered area were determined by the radius adjustable coverage mechanism of sensor nodes. An energy consumption threshold was introduced to enable nodes to adjust their radii according to their own situations, thus reducing the overall network energy consumption and improving node utilization rate. Finally, compared with the traditional ECA3D (Exact Covering Algorithm in Three-Dimensional space) and APFA3D (Artificial Potential Field Algorithm in Three-Dimensional space) by experiments, 3D-CAAR can effectively solve the problem of target node coverage in sensor network.