Abstract: Peptides are an important class of organic molecules in living organisms, and, together with proteins, they participate in biological processes. Peptides exhibit potent biological activities and functions and have been widely used in new materials, biomedicine, food, cosmetics, and other fields, holding tremendous social and economic value. In recent years, the rapid advancement of peptide synthesis technologies, especially chemical synthesis methods, has greatly accelerated the development and application of peptide products. As the number of peptide products on the market increases, there is a growing demand for the analysis of their biological activities. Simultaneously, the need for standardized quality control of peptide products has been recognized. Metrology, as the science of measurement, ensures that measurement results are reproducible and traceable, and plays a critical role in the development and production of peptides, as well as in the quality control of related products. Developing peptide/protein metrology—focusing on achieving accuracy and consistency in biological measurements and ensuring results are traceable to the International System of Units (SI)—is an urgent and challenging task for metrologists. This paper comprehensively introduces the chemical synthesis strategies of peptides, discussing the advantages, disadvantages, and application values of these strategies. Meanwhile, the development, applications, and challenges of peptide/protein metrology are also reviewed. This article intends to provide a reference for the quality control of peptide/protein products.