A study is conducted on the mechanical characteristics of buttresses under eccentric load to address the problem of uneven load distribution at the buttress bottom caused by hull deformation during immersed tube towing by the integrated vessel of the Shenzhen-Zhongshan Link,where traditional pressure monitoring methods based on a uniform-load assumption exhibit large errors (approximately 30%).By establishing a mechanical model of the buttress that considers linear load distribution along the vessel's longitudinal direction and introducing the eccentric load coefficient k,the stress distribution patterns of the buttress under different pressure levels and eccentric conditions are revealed,and a calculation formula for buttress pressure that reflects actual eccentric loading is derived,with a correlation coefficient exceeding 99.5%.The results show that when the eccentric load coefficient k≤7,the buttress stress is sensitive to variations in eccentricity.The proposed method is applied to back-analyze three typical working conditions,with all calculation errors of the resultant buttress pressure below 5%.Based on monitoring analysis of buttress pressures during immersed-tube floating transportation,it is recommended that the pressure of the bow buttress be controlled within 3,000-6,000 kN,the stern buttress pressure not exceed 5,000 kN,and the midship buttress pressure be maintained between 2,000-4,000 kN during ship-tube connection,providing a reference for the safety control of the ship-tube connection system.