Abstract: A new idea that the steel swirling flow in the mold is generated by adjusting the direction of jet from side holes in SEN is brought forwards, based on which a new type of multi-hole swirling flow nozzle, which is easy for machining and with simple structure, is designed.Three dimensions mathematical model is built for fluid flow and heat transfer in the round bloom continuous casting mold.The flow and temperature field are computed under traditional straight channel nozzle and the new type of swirling flow nozzle conditions.Study shows that the steel swirling flow can be formed in the mold by adjusting the direction of jet from side holes in SEN, and that the new type of swirling flow nozzle can obviously reduce the impact depth of the jet, accelerate inclusion floatation, move the heat center up, and increase the temperature on the meniscus.