Dynamic sensor deployment is one of the key topics in the research of WSNs. The performance of virtual force algorithm may be deteriorated because the stationary sensor nodes will confine the global optimal searching ability. Genetic algorithm is an efficient optimization tool for multi-dimensional optimization problems in acontinuous space with some disadvantages such as slow convergence and prematurity. This paper proposes a two-stage dynamic sensor deployment strategy in WSNs based on virtual force and genetic algorithm. That is, the algorithm firstly deploys the dynamic sensors in continuous larger area in WSNs in an approximate optimal way to produce high quality initial population by virtual force. Then GA is employed to achieve global optimization coverage of WSNs based on the result of the first stage. Simulation results demonstrate that the algorithm presented in this paper is effective and efficient.