Sensor network, which is made by the convergence of sensor, micro-electro-mechanism system and networks technologies, is a novel technology about acquiring and processing information. Wireless communication module is the most important component of the energy consumption on the WSN node boards, node identity is necessary in each communication with others. We consider the wireless sensor network (WSN) as a unknown anonymous network (UAN ) and analyze the disadvantage of assigning distinct identities which have been proposed to nodes of an UAN. The paper discusses the three phases of the identity assigning, then presents a new Layered Dynamic Identification Assigning (LDIA) algorithm for WSN, which is a distributed and energy efficient solution. The performance of the LDIA is verified under the NS2 simulation environment and in comparison with the DFS、0-1-Split 、L-P and W&L methods, and a number of experiments are performed under the NS2 Simulation Environment. The simulation results indicate that the proposed algorithm can satisfy the requirements for flexible deployment, low cost, high scalability and it is more effective.