Abstract: The design, selection and application principles of complex alloys according to the requirements of making low-alloy steels are discussed. The designed complex alloys containing calcium, barium, magnesium, strontium, rare earth elements, etc. should not only be able to deoxidize, desulphurize and refine liquid steel, but also alloy it. The application principles of alloys are as follows: using Si-Mn or Si-Mn-Al alloys for pre-deoxidizing, Si-Al-Ba or Si-Al-Ca-Ba alloys for final deoxidizing and Si-Ca-Ba-Mg(Sr) alloys for refining.