Aiming at the cold model test of argon protection on inject flow of steel casting, gas speed field around inject flow during argon protection was measured by particle image velocimetry (PIV) technique, and oxygen concentration around inject flow was analyzed by smoke analyze instrument. Furthermore, the effect of inlet height and inlet angle on protect effect was discussed. The results show that the better protect effect can be obtained through minimizing the inlet height and adopting inlet angle with 0 degree together with 90 degree.