Abstract: The Radon on earth comes from the decay of radioactive elements, which is colorless and odorless gas. Its concentration in underground enclosed space is significantly dependent on environmental conditions. The Radon restriction standards of European Union and China for indoor rooms, are 50 Bq/m³ and 100 Bq/m³, respectively. Radon is radioactive with a half-life of 3.83 d, and most of its decay daughters are metal particles, which are still radioactive. Long-term exposure of personnel to environments with high levels of Radon concentration can lead to radioactive diseases due to the radiation contamination of Radon and its decay daughters, most commonly respiratory tumors. The levels of indoor Radon pollution at home and abroad in recent years were reviewed, especially in typical underground enclosed spaces. Typically, the Radon pollution levels in subways were 1.2~166.5 Bq/m³, and the data of typical tunnels, mines, national defense engineering and underground laboratories were 105.3~4 434.2 Bq/m³, 1 952~5 121 Bq/m³, 39~17 169 Bq/m³, and 28~482 Bq/m³, respectively. It has been shown that Radon exceeds the standard more seriously in some enclosed spaces which are poorly ventilated or more difficult to ventilate. The development of the technologies of Radon protection and removal in enclosed spaces in recent years were also introduced. The characteristics of various technologies were analyzed, and proposed that isolation and protection of Radon, pressure swing adsorption separation and collection for Radon removal are more feasible ways and should be focused on the development of the research direction in future.