Aiming at the problem that the Wireless Sensor Network (WSN) is vulnerable to malicious attacks and the private key escrow problem caused by the existing identity-based cryptosystem, an Identity-based Dynamic Clustering authentication (IDC) algorithm was proposed. Firstly, PRivate Key Generator (PRKG) was avoided in the algorithm, the applicants' public key was generated by the PUblic Key Generator (PUKG), and the private key was chosen by the user himself separately, so that the key escrow problem in the identity-based cryptosystem was resolved completely. At the same time, the pseudo-secret matrix was generated dynamically by the algorithm, which could avoid collusion attacks so as to guarantee the security of the algorithm. Finally, in view of the differences in the resources owned by different nodes, the layered and hierarchical processing was used to complete the (un) signcryption at once, therefore reducing the node load of calculation and storage. The time consumption and energy consumption of the newly proposed IDC algorithm are reduced by more than 20% compared to those of the other three algorithms of the same type. In the term of algorithm robustness, when the network data packet increases rapidly, IDC algorithm performs more stably, which means the energy consumption is between 1 mJ and 10 mJ, with the span not more than 1.3 mJ. The time consumption of the algorithm is between 0.002 s and 0.006 s. Simulation experiments show that the newly proposed IDC algorithm is more suitable for the WSN with strict requirements on safety and energy consumption.