Abstract: The flashing liquid injection into another ambient liquid is two dimensionally simulated using a meshless particle method (called Moving Particle Semi-implicit(MPS) method). The numerical method has great advantage to compute interfacial and surface flows. It is the full Lagrangian description of fluid. Fluid is represented as moving particles, and the governing equations are transformed into particle interactions. The direct numerical simulation results are consistent with the experimental observations of highly expanding flashing jet into atmosphere. It is demonstrated that a flashing jet is worn away into a cone shape and the jet extinct length decreases with the increasing of pressure decay ratio of injection pressure to backpressure.