Abstract: Analyzed in the paper are the causes for all the major defects as occurring during the manufacturing process of the new type bainitic hollow steel, including crack and fracture of the hot-rolled bar, and defects of the hot-pierced-rolled hollow steel such as inner surface fold, outer surface double skin, inner surface decarburization and coarse-grained microstructure.Accordingly, preventive actions against such defects are proposed.It is concluded that the above mentioned in-process defects as staying with the bainitic steel bar and hollow steel can be prevented by means of establishing proper steel bar hot-rolling process and hollow steel hot-piercing/hot-rolling process based on an in-depth understanding of the microstructure and performance characteristics of the bainitic steel.