The air quality in public entertainment places such as underground KTV rooms was studied. Three KTV rooms in a city were tested about the indoor temperature, relative humidity, wind speed, CO2 concentration, radon, inhalable particles and the total number of colonies in different seasons, and the relevant questionnaire survey was conducted. The results show that air quality of the three KTV rooms is not optimistic, the relative humidity, CO2 concentration, inhalable particles and the total number of colonies of KTV room 1# and 2# as well as the temperature, relative humidity and wind speed of KTV room 3# are beyond the relevant standards. The analysis shows that the fresh air volume is the most important factor to affect the air quality in underground KTV rooms. The air quality can be improved by reasonably arranging fresh air volume, optimizing indoor airflow, regulating effectively indoor relative humidity, improving the filtration performance of air-conditioning system and reducing indoor air pollution sources, etc.