Messenger RNA (mRNA) has become a key focus in the development of therapeutic agents, showing significant potential in preventing and treating a wide range of diseases. The COVID-19 pandemic in 2020 has accelerated the development of mRNA nucleic therapeutics and attracted significant investment from global biopharmaceutical companies. These therapeutics deliver genetic information into cells without altering the host genome, making them a promising treatment option. However, their clinical applications have been limited by issues such as instability, inefficient in vivo delivery, and low translational efficiency. Recent advances in molecular design and nanotechnology have helped overcome these challenges, and several mRNA formulations have demonstrated promising results in both animal and human testing against infectious diseases and cancer. This review provides an overview of the latest research progress in structural optimization strategies and delivery systems, and discusses key considerations for their future clinical use.