Abstract: Combined with the actual production of a certain factory，analyzed the number，pattern，component of head slab，normal slab and different processing stages for ultra low carbon steel M2A1，found out the main reasons of the high inclusion content in the head slab. By optimizing the cast starting preparations，cast starting tonnage，Ar control，using stopper instead of common steel cast-starting pipe，optimizing the cast-starting speed curve in the tundish，and setting emergence time according to different sections，the quality of the head slab was improved. T[O]，[N] and inclusions contents was decreased along with the casting direction. T[O] content decreased from 0.0036% to 0.0025% at the position of 2.5m along head slab. And the total amount of inclusions decreased from 11.50mg/10kg to 8.26mg/10kg，inclusion number per unit area decreased from 8.73 mm^-2 to 6.26 mm^-2，and are close to those of normal slab after the position of 2.5m along head slab.

Key words: reoxidation, slag entrapment, stopper, casting-starting curve