To reveal the effect of different nozzle types on the initial flow of molten steel in the mold, a 410 mm × 530 mm billet mold in a certain plant was used as a prototype. Based on the similarity principle, the 1:1 water model has been established to compare the liquid level fluctuation and slag layer state under different casting speeds and immersion depths for the straight-through, five-hole and four-hole nozzle. According to the experimental results, it is found that the average wave height of the three nozzles ranges from 0.20 to 0.30 mm, 0.23 to 1.10 mm and 0.35 to 1.28 mm, respectively. The liquid level fluctuations of the five-hole nozzle and four-hole nozzle are more severe and the slag layers are more active than those of the straight-through nozzle. There is a slight entrapment but the steel is not exposed to the air, which is beneficial to the melting of mold powder and the removal of inclusions. The five-hole nozzle and four-hole nozzle have a stronger impact on the wall of mold than the straight-through nozzle, which is beneficial to the improvement of the central equiaxed crustal ratio. The best of immersion depth and casting speed with the multiple-hole nozzle are 170 mm and 0.38 m/min, respectively, which can ensure the smooth production and the improvement of bloom quality.