Provided is a method for preparing rutile from acid-soluble titanium slag, including: grinding acid-soluble titanium slag; adding a sodium carbonate modifier, and performing microwave irradiation treatment in a microwave device; adding an ammonium bifluoride additive; and performing acid purification and calcination to obtain rutile. By means of a microwave heating mode, the equipment investment needed by the method is low, and the energy consumption is low. The purity of artificial rutile is more than 91%, byproducts are fewer, and the environmental pollution is low.