The safety and economy of over-water construction are affected by the motion response and mooring performance of immersed subsea tunnel element on the sea.For a mooring project of tunnel element,we establish the numerical simulation model by hydrodynamics simulation software AQWA based on the 3-D potential flow theory and analyze the frequency responses of tunnel element.Considering the JONSWAP wave spectrum and current loads,we analyze the motion response and mooring performance in different directions of the environmental load and combined load.The result shows that the motion response of the immersed tunnel element is favorable in the high frequency region,and the response amplitude is small;the influence of currents for the element is enormous;the mooring force is more serious when the direction reaches 60 degrees.This study provides a theoretical basis for the design of mooring system design and construction.