In order to meet the size limit of the basin in model test, based on the static similarity principle, the length, stiffness and mass per unit length of the mooring lines are adjusted to give an equivalent horizontal truncation design scheme of the Tender Assisted Drilling (TAD) multi-floating body system, and the static and time domain analysis is carried out. The comparison results show that the horizontal restoring characteristics and dynamic simulation of the truncated mooring lines and each platform fit well with that of the full-scale calculation.