Abstract: The vertical pull-up characteristic of suction anchor is an important content to guide engineering practice. In order to solve this problem,the uplift characteristics of suction anchor in silty clay were studied,and the law of development and variation of earth pressure on the inner and outer walls of anchor barrel during uplift was revealed. The results showed that the earth pressure on the inner wall first decreases to negative pressure and then increases to positive pressure with the uplift height until it remains stable,and the ultimate earth pressure is less than the initial earth pressure;the earth pressure on the outer wall decreases approximately linearly;the failure mode is the bottom tension failure;based on the test results,the calculation can be more accurately determined according to the undrained shear strength and static penetration test（CPT）code. It is suggested that the shear strength coefficient alpha should be smaller when calculating the lateral friction of the outer wall of the anchor barrel. The theoretical calculation value of the tension resistance of the section soil at the end of anchor barrel is larger than the measured value. Under this failure mode,the maximum pull-up force of suction anchor increases with the increase of pull-up speed.