The overall stability of a port determines the project’s success or failure. The effect of the foundation with soft soil interlayer on the port’s stability can by no means be ignored. Taking Lvsi fishery port in Jiangsu as an example, the essay analyzes the impact of the soft soil interlayer on the overall stability of a port, sums up relevant rules and conducts tentative calculations with reference indexes offered. Moreover, it proposes solutions to the cases where the foundation does not meet the stability requirements, which serves as reference to the port’s design and construction in similar geologic situations.