In terms of individual elements, by-product minerals account for more than 60% of critical minerals in the United States and the European Union. Compared with the non-byproduct critical minerals, by-product critical minerals possess special geological and economic properties, which have a unique impact on their resource security. In recent years, as critical minerals have become the focus of the government and scientific research institutions, studies on the resource security of by-product critical minerals have increased gradually. This article presented a systematic analysis of criticality evaluation, supply mechanism, price theory, and international trade pattern of the by-product minerals. It is found that due to the important strategic position of the by-product critical minerals, the degree of companionality has become an important criticality evaluation index of minerals, so the security of supply of by-product critical minerals has been ensured to some extent. The supply of by-product critical minerals depends on the change of supply and demand of their main minerals, which leads to inelasticity of supply and faced with supply risk. At the same time, the geographic distribution of by-product critical minerals is highly concentrated, which causes higher trade risks in global trade. Compared with non-byproduct critical minerals, by-product critical minerals have higher price volatility and their price volatility is affected by that of their main minerals , and there is a risk to stabilize the supply and demand of by-product critical minerals. Finally, in light of the background and trend of future economic development, this study identified the research direction of the resource security of by-product critical minerals in the future.