The development of the Internet of Things (IoT) is on the basis of the secure information transmission, and the same is true for the numerical control system (NC system) based on the IoT (IoT-NC system). If the information is stolen in the process of transmission, the IoT-NC system will not be practical. Compared with the IPSec, the IDSec proposed by this paper is independent with other protocols, which is conducive to further expansion and compatibility, and it could better solve the compatibility problem of the IPSec with the NAT. From the view of transfer process, the IDSec removes the cumbersome process of add and removal IP and TCP header in the IPSec, which will reduce the amount of processing time and transmit data. In the meantime, the IDSec also retains many advantages of the IPSec, such as integrity authentication, origin and destination address authentication, anti-monitoring service, anti-replay service and so on. So, the IDSec is more suitable than the IPSec for the secure information transmission in the IoT.