Abstract: A series of model tests in sand under 1g condition were conducted to investigate the influence of spudcan penetration on an adjacent pile group. Behaviors of piles with fixed pile head constraints were observed, and the pile spacing was selected as 2.5 times the pile diameter during the tests. The changing pattern of the pile shaft bending moment with spudcan penetration into the soil was analyzed by comparison of the maximum bending moment along the pile near the spudcan in the adjacent pile groups before and after spudcan penetration, and the response of a single pile with the same clearance was compared as well. The growth rate of the maximum bending moment of the pile group relative to the maximum bending moment of the single pile body was defined at the same time as the flexural strength ratio. The influence of spudcan penetration on pile group effect and the influence of clearance on the pile group effect were studied through the flexural strength ratio. Compared with the pile group effect before spudcan penetration, it is indicated that spudcan penetration weakens the pile group effect; and the influence of spudcan penetration on the pile group effect is weakened with the increase of clearance, when the clearance exceeds one time the maximum spudcan diameter. It is recommended that the influence of spudcan penetration on the adjacent pile group can be ignored. This study can provide useful guidance to investigate the influence of spudcan penetration on an adjacent pile group.