In this paper, we propose a cooperative control method of a single-user multi-robot (SUMR) teleoperated system for maintenance in offshore plants that is designed to perform in a 1:N mode (here, 1 refers to the number of user, and N denotes the number of slave robots), in which a single user teleoperates a number of slave robots directly to conduct a specific operation or in an autonomous cooperation mode between slave robots in order to overcome the limitation of the 1:1 teleoperation mode. This paper is also designed to extend compatibility in the SUMR teleoperated system's controller. A haptic device, which is one of the master device, is used for duplex transmission of control and status data between a robotic manipulator and user. In this paper, a new haptic library is also designed to connect between a haptic device (PHANToM premium, Sensable) and a controller based on LabVIEW. The designed new haptic library (DLL, dynamic linking library) that is created using C++ is called in LabVIEW, which is a GUI (graphical user interface) based software development tool.