Abstract-Tensioner for deep water pipe-laying vessel is a type of engineering equipment that is applied in sub-sea pipeline laying. Based on the designed tensioner body for Slay vessel, with the capacity of 200t and can meet the requirements of 3000m water-depth pipe-laying, the corresponding monitoring and controlling system need to be designed. Firstly, the programs of on-line monitoring and controlling system are proposed, and then the software and hardware of the system are designed. In addition, the manmachine interaction interface of the system is developed. This research could provide the guidance for the design of the on-line monitoring and controlling system of 200t tensioner. The test is carried out to verify the functions of the designed on-line monitoring& controlling system. The test results show that the designed system is reliable and also have good maneuverability.