Research on the key parameters of tube mold for rail steel bloom was carried out in this paper, the effects of cooling water on bloom quality was studied, the effects of tube mold on magnetic intensity of electro-magnetic-stirring was analyzed, the shielding effect of tube mold on stirring intensity was represented by comparing solidification structure, suitable stirring parameters was confirmed; the effects of tubular corner size on cooling of bloom corner was analyzed by taken simulate calculate, and explore the effects of taper on the casting amount of steel by carried out experiment, parameters have been worked out and quality of bloom corner have been improved at last, convex hull of corner have been eliminated and zero defect for corner was realized, mean squared error of segregation degree at corner and solidified shell is not more than 0.010, better than combined mold remarkably.