Energy is the determinant factor for the survival of Mobile Sensor Networks (MSN). Based on the analysis of the energy distribution in this paper, a two-phase relocation algorithm is proposed based on the balance between the energy provision and energy consumption distribution. Our main objectives are to maximize the coverage percentage and to minimize the total distance of node movements. This algorithm is designed to meet the requirement of non-uniform distribution network applications, to extend the lifetime of MSN and to simplify the design of the routing protocol. In addition, test results show the feasibility of our proposed relocation algorithm.