Abstract: Cohort studies play an important role in elucidating the association between risk factors and diseases， and are widely used in etiology research， the assessment of disease prognosis， understanding the natural history of diseases， and the surveillance following the market release of new drugs. The data produced by cohort studies possess great scientific value and can provide essential evidence for public health practice. A well-conceived scientific design is a prerequisite to conducting a cohort study， and the design should focus on aspects such as sample size， selection of exposed and non-exposed populations， follow-up procedures， outcome assessments， research duration， and the choice of analytical indicators and methods. Cohort studies have become an important way to obtain scientific evidence. Internationally renowned population-based cohorts， such as China Kadoorie biobank and the Framingham heart study cohort， have provided a wealth of scientifically valuable evidence for promoting human health. The quality of data produced by a cohort study is extremely important， and a cohort study should continuously incorporate new technologies and methods to provide objective， accurate， and reliable means to determine exposure and outcomes， as well as control for bias. Cohort studies have great potential for application and will continue to provide abundant high-quality scientific evidence for the development of strategies and measures to enhance human health.