Objective  This paper aims to study the damage modes of the target simultaneously caused by multiple damage elements, and analyze the damage effect of the cylindrical shell subjected to the double underwater explosion (UNDEX).

  Methods  First, a finite element model of cylindrical shell is established, and arbitrary Lagrangian-Eulerian（ALE） method is used to investigate the damage characteristics of cylindrical shell under underwater explosion of single or double explosion sources, and the damage effect is evaluated from the structural fracture area, the maximum vertical displacement of the structure and the area of the plastic strain area.

  Results  Take 500 kg TNT charge as an example, the calculation results show that, when the spacing between two explosive sources is 1 m, the damage to the outer plate of the cylindrical shell is more serious when the double explosive source is equal to that of the single explosive source, but the damage to the inner plate of the cylindrical shell is less than that of the single explosive source. At the same time, with the increase of the distance between the two charges, especially when the distance is greater than 3 m, the damage effect on the cylindrical shell structure becomes weaker.

  Conclusions  By calculating the damage to cylindrical shell structures by underwater explosion under different initial parameters, the general rules of damage to cylindrical shell structures by single and double explosion sources are given, which can provide reference for enhancing the power of underwater combat weapons.