The embodiment of the invention discloses a semi-steel dephosphorizing method. The semi-steel dephosphorizing method comprises the steps that scrap steel and lime are added into molten iron; and blowing is conducted in a mode combining the staged oxygen lance flow with the staged bottom blowing flow, wherein according to the mode combining the staged oxygen lance flow with the staged bottom blowing flow, in the earlier stage, the first oxygen lance flow is 25000-35000 Nm<3>/h, the first lance height is 2.4-2.6 m, and the first bottom blowing flow is 1000-1200 Nm<3>/h; in the middle stage, the second oxygen lance flow is 25000-35000 Nm<3>/h, the second lance height is 2.0-2.2 m, and the second bottom blowing flow is 2000-2400 Nm<3>/h; and in the later stage, the third oxygen lance flow is 18000-25000 Nm<3>/h, the third lance height is 1.5-1.7 m, and the third bottom blowing flow is 3000-3600 Nm<3>/h. By adoption of the semi-steel dephosphorizing method, the technical problem that in the prior art, a dephosphorizing method is poor in dephosphorizing effect is solved.