In order to improve bias flow， jump bar and water plugging phenomenon during ultra-low carbon steel continuous casting process in a factory， through the tunish breathable on the nozzle， plug rod and immersion nozzle such as continuous casting function resistant material improvement， switch the air top nozzle to switch to special diffusion breathable material， blowing into the argon bubbles along the nozzle form uniform air curtain. The surface stomatal rate is 5.2% higher than that before the improvement， which prevents the accumulation of inclusions in the inner wall of the nozzle and alleviates the clogging of the nozzle. One argon hole located in center is changed to six holes of stopper rod， which can realize 360° even argon blowing around its head and decrease inclusion collection on the head. The SEN adopts merterials of carbon free， low aluminum， high silicon content. These refractory can react with the inclusion on the wall of SEN， which prevents its clogging. After the application of improved resistant materials in ultra-low carbon steel， the number of jumping rods per casting is reduced by 0.83 times and 31.8%， the frequency of online replacement of SEN caused by nozzle plugging is reduced by 0.38 pieces and 41.3%， and the control accuracy of crystallization level is stabilized， the qualified rate of cold rolled coil inclusion is improved by 0.238%， and the number of single tunish casting heats is increased by 0.53 heats and increasing by 8%， thus optimize the flow field of mould. It is proved to put forward to optimize 1 000 mm-2 200 mm caster’s mould flow field.