In order to study the influence factors of composite foundation settlement of soil-cement mixing pile and provide guidance for optimizing foundation design, ABAQUS finite element software was used to conduct 3D modeling of composite foundation based on a port project in Guangxi province. The rationality of the model was verified by combining with the static loading test data. The influence of cement content, pile spacing and cushion on foundation settlement was further discussed. The results show that increasing the cement content can reduce the settlement value of composite foundation to some extent, but the effect is worse than that of decreasing the pile spacing and setting the cushion. The settlement value of foundation can be reduced by shortening the distance between piles. Pile spacing should be scientifically selected according to the requirements of site loading. By adjusting the thickness and elastic modulus of the cushion, the bearing capacity of the foundation can be improved and the settlement value can be reduced, and both should be considered in design.