In recent years, patient-focused drug development (PFDD) has received widespread attention as a new paradigm in clinical trials. The PFDD emphasizes patients are partners in research projects, where patients can participate in research design, implementation, and outcome measurement, rather than just providing data. PFDD has shown great value in the research and development of pharmaceutical products, such as in accelerating the process of patient enrollment and improving the success rate of drug approval. Many countries and regions, including the United States, China, and Europe, have issued relevant regulatory policies and guidelines related to PFDD, covering study design, implementation, and risk-benefit assessment. The core of PFDD implementation is clinical outcome assessment (COA), of which patient-reported outcome (PRO) is most common. As far as the US Food and Drug Administration is concerned, there are numerous COA tools waiting for qualification, but currently all qualified are PROs. This review focuses on PRO and explores the key elements of PRO instruments' development, application, and inclusion in regulatory decision-making.