The invention discloses a method for producing high-grade titanium slag through low-grade rutile by adopting a tunnel kiln reduction method. The rutile and anthracite powder are evenly mixed at first, are directly put into a refractory tank after mixing, and then enter a tunnel kiln at the constant temperature of 1100-1200 DEG C for 20-30 h; and materials are discharged from the refractory tank after reduction and cooling, and then crushed after being discharged, and crushed materials are subjected to electric separation through an electric separator, a double-roller high tension separator is used as the electric separator, and the high-grade titanium slag is obtained. The method has the advantages that the process is simple, energy consumption is low, the cost is low, the yield is high, and volume production can be conducted according to actual demands. The content of TiO2 of the produced high-grade titanium slag can be up to 95% or above.