The invention discloses the application of coal gangue used as a converter slag inhibiting agent, and a converter slag inhibiting method. According to the method, coal gangue is used as slag inhibiting agent base materials; when slag inhibition is performed during blowing, steel of 1-2kg/ton is added every time; when slag inhibition is performed during furnace inversion and steel tapping, steel of 0.2-0.5kg/ton is added every time. A good slag inhibiting effect can be reached by a small quantity of the slag inhibiting agent, and the splash during converter blowing can be effectively controlled. Because the price of raw materials is low, and a processing technology is simple, the cost of the slag inhibiting agent only accounts for 10-30% of that of a conventional technology; the waste of raw coal or magnesium resources is effectively avoided. Aiming at the problems of over-high soft blowing of iron oxides during blowing, difficult converter inversion at a blowing end, and slag overflow in steel tapping after reblowing, according to the method, the slag inhibiting agent is added, so that slag iron oxides can be effectively reduced, and the purposes for controlling splash and quickly tapping steel are reached. The method does not have bad influences on the environment, and besides, resources are saved, and cost is reduced, so that the method has a popularization and application value in steelmaking production plants.