According to the mechanism of crack formation of blooming, blooming process control method. By controlling the surface crack of slab to reduce the amount of finished steel crack scrap. Needs to be pointed out is the first step to control the composition of molten steel, which is the premise of quality control of blooming, especially n, Nb content control, Nb and carbonitride precipitation caused by grain boundary embrittlement and the brittle zone to the high temperature expansion, when the Nb content can reach 0.01% crack on a sharp increase in the.