The invention provides a process for preparing fumed silica and recovering metal with nickel tailings as a raw material. In the process, the nickel tailings and other kinds of waste are used as the raw material and react with fluorine-containing acid liquor, hydrochloric acid and nitric acid to prepare high-value-added products fumed silica and recover metal such as gold, silver, copper and iron, the content of SiO2 in the prepared product is larger than 99.9%, the specific area measured through a multi-point BET method is 350 m<2>/g or more, and the effect of turning waste into wealth is achieved. Acidic gas generated in the preparation process is absorbed through a negative pressure water absorbing tank to prepare corresponding acidic liquid, and when concentrated to certain concentration, the acidic liquid can be used circularly. The invention further provides a production device used in the process, parts used in the production device are common tools used in a chemical plant and low in cost, and large-scale industrial production can be achieved.