In the environment of intelligent manufacturing and “Industry 4.0”, the intelligent manufacturing line as an important carrier of intelligent manufacturing has high research significance in its algorithmic IT operations, condition monitoring, and data acquisition. This article designs an identity authentication method called R-ECC (Random-Elliptic Curve Cryptography) for the mobile terminal of intelligent manufacturing line, which is based on the security model provided by OPC UA. The method addresses the problems of limited communication resources and high security requirement of data transmission in the process of communication between an Android-based mobile terminal and OPC UA server. This method introduces random numbers and elliptic curve cryptography in the authentication process, which improves the security of OPC UA identity authentication and reduces the consumption of communication resources in the same time. The experimental results show that the R-ECC identity authentication method for the mobile terminal of intelligent manufacturing line can effectively improve the security of the authentication process, reduce the hardware resource consumption of the mobile terminal, and accelerate the speed of identity authentication.