Molecular nuclear medicine is a new subject that uses nuclear medicine technology to study the changes of molecular level in organisms in order to understand their functional changes. 2021 Radiological Society of North America annual meeting has more than 40 academic reports on molecular nuclear medicine. The main content includes new tracers and new imaging methods in tumors (prostate cancer, breast cancer, rectal cancer, etc.) and other diseases (Coronavirus Disease 2019 (COVID-19), Alzheimer′s disease, Parkinson′s disease, etc.). This article reviews the relevant research progress.