Abstract: The void coalescence and interaction in dynamic tensile fracture of ductile metals were investigated by using axial symmetric finite element analysis. The influences of initial ligament distance between voids and loading strain rate on the void coalescence process were discussed. The start time of void coalescence was estimated quantitatively through correlated shape evolution of the voids. The measurement results show that the critical ligament distance at the start time of coalescence is approximately a half of void diameter, which is independent of initial separation distance between voids and strain rate. In reality, the voids may interact through their plastic fields. However, a critical plastic strain threshold in the ligament zones is needed to drive the void coalescence. Assuming that the voids are uniformly distributed within the damaged material, the critical ligament distance are consistent to the critical porosity in physical essence, and can be transformed each other.