A large eddy simulation of unsteady argon/steel two phase flow in a continuous casting mold is presented in this work. The inhomogeneous Euler-Euler approach is used to describe the equations of motion of the two phase flow. Large eddy simulation model is used to solve the turbulent viscosity force. The drag force, lift force and virtual mass force are incorporated in the model. And this model has been validated with a water model experiment and the measurements of the ultrasonic flaw detection. The predicted unsteady two phase turbulent flow characteristics were validated, indirectly, by the measurements of ultrasonic flaw detection. The predicted asymmetric flow was validated by the water model experiment. The simulation results show that the distribution of the bubble diameter is seen to depend on the argon gas and molten steel flow rates. The mean bubble diameter decreases with increasing the molten steel flow rate, but increases with increasing the argon gas flow rate. The asymmetric flow inside the mold was not stationary; the time intervals for changeover appeared to be vary random. It can be concluded that the shape of the bending part of the secondary cooling zone of mold is important to the asymmetric flow. The asymmetric flow occurrs near the bending section.