Abstract: An Al-Ca-based conditioning flux was newly developed and the comparative experiments were carried out between the conventional Al-CaO-based and the Al-Ca-based conditioning fluxes to control the tapping slag in ladle for the 180 t BOF at a certain steel plant. Then, the effects of the two conditioning fluxes on the slag and both the Al-killed and unkilled molten steel were investigated. The results indicated that 200 kg of the Al-Ca-based conditioning flux is equivalent to 400 kg of the Al-CaO-based conditioning flux for each melt in the BOF, and no obvious increase in carbon content is found in molten steel no matter which conditioning flux is used. In addition, if the conditioning effect remains the same, the Al-Ca-based conditioning flux is more convenient for ladle refining with the cost reduced significantly.