Abstract: The nonlinear dynamics of a gas bubble near the free surface and the cylinder is three-dimensionally computed. The flow field is supposed to be irrotational and incompressible at the underwater explosion impulsive phase. The high-order curved triangular elements are used to disperse the three-dimensional bubble surface. The evolution of the bubble is solved by the boundary integral method, and the singularity of the double layer potential is eliminated by recasting the principal-value integral of the double-layer potential. So the computational result will be more accurate. The real velocity at every node on the boundary surface is solved precisely via the reasonable weighing method, and the elastic mesh technique (EMT) is applied to get the optimum velocity. The mesh-smoothing algorithm is no need during the whole simulating process. Comparisons show that the results by the three-dimensional model are in agreement with those by the axisymmetric model. The present three-dimensional model is used to simulate the interaction between the bubble and the free surface near the cylinder. The behavior of the bubble is strong nonlinear under the combined influence of the free surface and the cylinder.