The invention discloses a continuous casting process for a bainite steel billet. The process comprises the following steps that in a continuous casting soft reduction region, the press quantity is controlled through change of casting billet center solid fraction fs, wherein the relationship between the press quantity of soft reducing a rack is that when fs is larger than or equal to 0 and smaller than or equal to 0.20, the press quantity is 0mm; when fs is larger than or equal to 0.2 and smaller than or equal to 0.3, the press quantity is 1.8mm; when fs is larger than or equal to 0.35 and smaller than or equal to 0.45, the press quantity is 3.2mm; when fs is larger than or equal to 0.50 and smaller than or equal to 0.60, the press quantity is 4.3mm; when fs is larger than or equal to 0.65 and smaller than or equal to 0.80, the press quantity is 5.7mm; and when fs is larger than or equal to 0.8 and smaller than or equal to 1, the press quantity is 0mm. According to the process, the press quantity is controlled through change of casting billet center solid fraction, so that the defects of central segregation, central porosity, central pipe and the like of the casting billet are relieved and eliminated.