Abstract: Based on the coupled model of turbulence and multiphase fluid flow, the flow behavior with free surface fluctuation in a bloom casting mould was numerically simulated. The influence of nozzle outlet angle on the fluid flow and free surface oscillation in the mould was analyzed. The results show that when the downward nozzle outlet angle increase by 5°, the impinging spots descend by 13 mm and 10 mm at the wide faces and narrow faces respectively. At a given submergence depth of 100 mm, outlet angle show limited influence on the fluctuation within 3 mm. The fluid close to mould wall is more active than that close to nozzle. The nozzle outlet angle of 20° is recommended to use.