The type of multi buoy moorings (MBM) is commonly used in offshore mooring of tanker.We summarize basic design issues related to MBM design,including applicable standards,general layout,wave loads,mooring analysis.Based on comparative study of domestic and international standards and simulation of a real project with OPTIMOOR software,we give typical layouts of MBM,methods of vessel loads calculation and mooring analysis.The results show that using OPTIMOOR as dynamic simulation analysis software and frequency domain analysis can effectively design and optimize the MBM design.