A three-dimensional dynamic simulation model of the molten iron flow field was presented in the paper with Fluent simulation software. Different operating parameters combinations, including different oxygen lance locations, oxygen pressures and oxygen flows, different arrangements of bottom blowing holes, hole sizes, nitrogen pressures and nitrogen flows were studied. It is shown that the relative optimum value of the distance from top-blow gun to the molten iron surface is 1500 mm, and bottom blowing hole diameter is 20mm, there is no significant difference of the blowing effects found when comparing single ring arrangement with double rings arrangement of 8 bottom blowing holes with only bottom-blow, and the bottom-blow of inner ring is disturbed by top-blow when top and bottom combined blow. Optimized design results have been applied to the design and manufacture of the actual converter, the converter has been successfully used in plant. The actual production results indicate that the desiliconization precision can reach 0.05%, the content of Cr2O3 in the slag after reduction can be less than 2%, better than the technical requirements of 3%, and improve the recovery rate of the chromium. Compared with traditional desiliconization method by iron gutter and iron ladle, desiliconization by converter does not use compression residue agents and reduce the amount of desiliconization agents and slag, and improve the desiliconization efficiency and productivity.