Wireless sensor networks（ WSNs） are constrained by limited battery energy

and it can be solved by recharging sensor nodes periodically through wireless energy transfer technique which would make sensor nodes remain optional persistently. For 3-dimensional（ 3D） WSNs

an optimization problem is proposed

after proving that the optimal traveling path for the wireless charging device is the 3D shortest Hamilton cycle

the continuous timevarying model were proposed. Simulation results indicate that the network lifetime has been extended indeed.