Abstract: In addressing the challenge of assessing the strength of soft clay in the foundation design of offshore wind turbines,this paper focuses on the strength calibration of soft clay in Zhejiang Jiaxing’s offshore region by ball penetration tests and laboratory test results.The ball penetration factor N_ballfor moddy silty clay was obtained.The ball penetration factor N_ball,DS,determined through consolidated quick shear tests,is ranged from 6.70 to 14.91,with a mean of 10.58 and a standard value of 10.91.Likewise,the factor N_ball,UU,determined by using triaxial unconsolidated undrained shear test results,is ranged from 7.75 to 23.75,with a mean of 17.44,and a standard value of 19.03.The calibrated ball factor N_ballprovides a more accurate representation of the soft clay strength in Zhejiang Jiaxing’s offshore area.We recommend adopting N_ball,UUwith a standard value of 19.03,calibrated from the triaxial UU test,as the parameter for interpreting the lower limit of strength.Additionally,N_ball,DSwith a standard value of 10.91,calibrated from the consolidated quick shear test,serves as the parameter for interpreting the best estimate（median value）of strength.