Based on the data of realtime records the tensile directions na-mely the angle between the tension line and the vertical line, while the inclining moment is up to the maximum which normally occurs in the end of hauling，are-analyzed, when and the purse-line is supposed as a suspended flexible wire in the water during hauling. On account of the amount and the point of tension and other factors，a simplified formula of maximum inclining moment is derived.The rolling of seiner is calculated with the impulse response method according to the rolling equation. For different size of vessels and net specifications，the adjustment coefficients，C₁ and C₂，are introduced into vessel's inertia moment.of the mass for rolling and for net specifications respectively in the calculation. In practice, the results from calculation are satisfactory. In this paper, it has indicated that rolling amplitude will increase many times if the fishing vessels are effected by the moments caused by wind and/or wave during hauling, and the vessels might be in danger. The calculation as mentioned about is practically significant in the designing of purse seiner and the checking of its stability. This method provides a basis for the further modification and adjustment of tha Rules for stability of fishing vessels.