To overcome the problem that the security capabilities of the communication deteriorate significantly in the presence of eavesdropping, malicious behaviors and privacy disclosure of user platform in wireless service system of IoT, a secure transmission model among clusters is proposed based on the trusted third party. A model for trusted authentication and mechanism for the enquiry of cluster address are constructed based on the condition of discrete logarithm problem and the bilinear mapping. This model generates the temporary identity according to the Hash function and random number to achieve anonymity and only provides enquiry service to the trusted clusters authorized by control center. The suppression of Rudolph attack between user platform and coordinator is taken into consideration by setting the trusted third party in authentication mechanism. In accordance with the key agreement between source cluster and clusters in the link, certificate validation and data filling mechanism, the nested encryption and decryption and flow analysis defense are achieved to guarantee the transmission security among clusters. On this basis, the security proof of data transmission model is presented. The theoretical analysis and experimental results show that the developed model performs well in terms of eavesdropping suppression, flow analysis inhibition and anonymity protection.