Abstract: Radio-LC-MS is an on-line analytical system, which is composed of liquid chromatography (LC), ultraviolet absorbance detection (UV), radioactivity monitor (RAM) and mass spectrometry (MS).The RAM is sequentially connected between the UV and MS using a heterogeneous (solid) flow cell. If a homogeneous (liquid) flow cell is used, the flow is split to both the RAM and MS. Radio-LC-MS is a valuable tool for studying of radiopharmaceuticals. This review covers the application of Radio-LC-MS in radiopharmaceuticals, including structure identification, metabolites analysis, quality control and so on.