The sharp-interface model is expected to improve accuracy and efficiency for directly simulating gas-liquid two phase flows, but it is quite challenging for Eulerian mesh methods. This study aims to propose an exact sharp-interface model for bubble simulations with interface coalescence and breakup based on Lagrangian particle methods. In the proposed sharp-interface model, the gas and liquid phases are calculated separately based on an accurate and stable moving particle semi-implicit method with advanced free-surface detection technologies [1]. In this manner, the discontinuous jump of density and viscosity across the interface is permitted. To calculate the physical bubble pressure, weak compressibility is considered in bubbles. Therefore, a new weakly-compressible Pressure Poisson equation (PPE) is proposed for the gas phase. To realize the exact sharp-interface model, the interface tension is newly considered as a pressure boundary condition at the free surfaces of the liquid phase rather than the conventional volumetric force in a transitional region. In this manner, no surface tension is smeared to the gas phase. The free-surface tension model in the authors’ recent study [2] was employed for the calculation of the liquid phase. To avoid the unphysical interaction between two adjacent bubbles, the bubble connectivity is detected, and only the interactions of gas particles that belong to the same bubble are allowed. The bubble rising simulations in 2D and 3D verified the proposed method. Numerical examples demonstrated the proposed method could produce more physical result in simulating the fast deformation of the bubbles with sharp angles. Finally, the advantages of the proposed method for simulating bubble coalescence and breakup are demonstrated via the comparison with the results using OpenFOAM. In brief, the sharp-interface model could produce more accurate results in simulating the topological changes of bubbles.