The occurrence of coverage-hole (CH) in a wireless sensor network degrades the performance of the network in terms of data transmission. Therefore, after the detection of CH, hole-patching is the next important task in order to reduce the energy consumption and to improve the network lifetime. In this paper, we propose an improved coverage-hole patching technique (CHPT) based on the concept of center of tree. The prerequisite to hole-patching is the hole-detection, which is done based on Delaunay Triangle and empty circle property. Subsequently, using the Inner empty circle property, the hole-area is estimated. And finally, CHPT is used to determine the hole-boundary and formulate the sub-trees for identifying the patch-positions to be covered by deploying additional sensor nodes. Experimental results show that the average percentage of coverage in CHPT increases up to 98.6% in terms of additional sensors and with a given sensing radius.