The invention discloses a foaming agent for stone-powder-doped foam concrete and a preparation method thereof. The foaming agent includes foaming agent mother liquor, and may also include a foaming assistant, a curing agent, a foam stabilizer and water. The preparation method of the foaming agent disclosed by the invention is simple, and raw materials can be widely purchased. Compared with the conventional foaming agent, and the foaming agent solves the problems of poor homogeneity, collapse deformation and cracking and the like of the foamed concrete caused by the incorporation of stone powder.