In order to solve the problem of breakage of mooring ropes due to excessive instantaneous tension when large ships are berthed,a shore-based constant tension mooring device was proposed,in which the volume-changing constant tension hydraulic control principle was adopted.The main content included design requirements and work principles,theoretical calculations,key component selection,mechanical structure design,hydraulic system design,and system simulation.The analysis results show that this mooring device can control the mooring rope tension within a relatively fixed range without changing the existing mooring facilities and cables,thereby ensuring that the cables do not break and can be installed separately.It requires very little energy and is economical and practical.