The semi-submersible bottom-supported offshore wind turbine installation vessel suitable for the operation in offshore shallow water area is of the characteristics of good safety, high construction efficiency, and low cost, and the particularity of its design lies in the need to consider the loss of sit-on-bottom area caused by the ocean currents eroding sediment. Taken a typical actual ship developed as an example, the main functions are expounded, two operation conditions that should be considered for the sit-on-bottom stability are proposed, the structural strength of sit-on-bottom operation condition is checked with the finite element calculation, and the corresponding measures are given for the operation under the two geological conditions of ooze and silt, which can provide certain technical reference for the design of same type of vessels.