The utility model relates to a flow stabilizing device for feeding of a magnetic separator, and in particular relates to a flow stabilizing box for a magnetic separator. The flow stabilizing box comprises a box body, wherein a loading pipe is arranged on the end surface of the bottom end of the box body; a feeding pipe is arranged on the end surface of the top end of the box body; an overflow pipe is also arranged on one side surface of the box body; a valve is also arranged on the overflow pipe; and the caliber of the feeding pipe is 219mm. The utility model provides a flow stabilizing box for a magnetic separator. The flow stabilizing box is capable of providing a buffer space for a thin medium which flows into the magnetic separator; the problem of low magnetic separation efficiency caused by excessive feeding quantity of the magnetic separator is avoided; and when the thin medium cannot be buffered in the box body, an excessive thin medium can flow back to a thin medium barrel through the overflow pipe, so that the magnetic separator can normally work; and the problems that the flow of a thin medium pump and the handling capacity of the magnetic separator cannot be easily matched, so that a feeding valve of the magnetic separator is high in wear rate and frequent to replace are solved.