The invention relates to a method for producing acid-dissolved titanium slag powder through a direct granulation method. According to the method, the acid-dissolved titanium slag powder is prepared by adopting a following granulation device, wherein the granulation device comprises a molten metal injection structure, a rotary granulation system, a cooling system and a water circulation system; the molten metal injection structure is used for injecting acid-dissolved titanium slag into the rotary granulation system; the rotary granulation system is used for granulating the acid-dissolved titanium slag; the cooling system is used for cooling particles produced in a granulation process; the water circulation system is used for collecting and recycling cooling water; and the acid-dissolved titanium slag particles obtained by adopting a preparation device are collected into an acid-dissolved titanium slag powder collector and are crushed through a ball mill to obtain titanium slag powder of which the particle size is less than 0.04mm and the proportion is more than 98%. Generation of a rutile phase can be inhibited as much as possible when the acid-dissolved titanium slag powder is produced by adopting the method, and the production efficiency is higher.