The invention relates to the field of titanium-containing slag smelting methods, and particularly relates to a method for preparing titanium carbide slag by using titanium-containing slag which shortens reaction time and reduces smelting power consumption. The method comprises the following steps of, a, adding titanium-containing slag into a submerged arc furnace or an electric arc furnace and increasing the temperature; and when the temperature reaches a set value, adding a carbonaceous reducing agent, and making the carbonaceous reducing agent react with the titanium-containing slag in the furnace; b, taking a flue gas temperature and a CO concentration value in the furnace as a judgment basis of a reaction control, and adjusting an input power and a feeding speed of the reducing agent according to the flue gas temperature and the CO concentration value in the furnace, thus making the CO concentration value the control reaction maintain the optimal stable state; and c, ending the feeding of the reducing agent; and when the CO concentration value gradually falls to the set concentration, starting slag tapping, ending the reaction, and obtaining the titanium carbide slag. Accordingto the method, the reaction time can be shortened, the smelting power consumption can be reduced, and the technical economy of preparing the titanium carbide slag by using the titanium-containing slag is improved; and the method is particularly suitable for the process of preparing the titanium carbide slag by using the titanium-containing slag.