Four-hole submerged entry nozzles (SEN) with different structures were researched using the water simulation test by particle image velocimetry (PIV) and DJ800 hydraulic measurement system to get suitable SEN for high efficiency continuous casting. The influences of the exit area ratio (2∶1∶2, 3∶2∶3, 1∶1∶1 and 1∶2∶1), upper guide island angle θ (20°, 40°, 60° and 80°), and lower guide island angle α (60°, 80°, 100° and 120°) on the vortex position in the mold and fluctuations were researched. The results show that the exit area ratio and the upper and low guide island angles have obvious influence on the flow field; the flow field in the mold is suitable at 1∶2∶1 of the exit area ratio, 80° of upper guide island angle, and 100° of lower guide island angle.