Abstract: In this paper，a non-linear finite element analysis is performed to investigate the ultimate loading capacity of beams with web openings，which is a problem that must be considered before the laying of cable ducts in hull structures. Particularly，a deck web beam under uniform transverse load is examined， with different influencing factors on the loading capacity being discussed，including the shape，size and location of the web openings. A formula is then proposed to predict the ultimate loading capacity of a beam with long-circle openings，which is seen to be highly consistent with numerical results. In brief，the formula presented here makes a good reference for future design of beams with web openings.