Abstract: The reason and countermeasure of "ridging"defect on the surface of stainless steel products is clarified,the advantages and disadvantages of various methods to improve the solidification quality of the casting billet are analyzed. Based on the previous theoretical and experimental results,the idea of refining the solidification structure of ferritic stainless steel with the composite core containing titanium is proposed and an industrial experiment is carried out.The result shows that the proportion of equiaxed grains without Ti addition is about 30%,while the proportion of equiaxed grains with 0. 15% Ti addition is above 85%.Through counting the cores containing-Ti in the different regions of the cast billet,it can be found that 50%of the cores in the columnar grain zone is Mg-Al-Ti（ O,C）,the cores in the CET zone are mainly composed of Ti（ C,N）,Ti N and Mg-Al-Ti（ O,N） where the outer layer of the cores is Ti N,the cores in the equiaxed grain zone are mainly composed of Ti N.The results of the industrial test further prove that the core containing-Ti is the main reason for the refinement of solidification structure of the ferrite stainless steel.