Objective To investigate the hygienic status of ventilation systems in centralized air-conditioning in Nanshan district of Shenzhen City, and to provide a basis for standardizing hygienic management and targeted prevention and control. Methods According to the requirements of ^"Hygienic Specifications for Central Air Conditioning and Ventilation Systems in Public Places^" WS 394-2012, 303 public places using central air conditioning and ventilation devices in Nanshan District of Shenzhen City were sampled from 2016 to 2019 for four consecutive years. From these, 19 large public places were randomly selected for investigation of the hygienic condition of the air supply system. Results The qualified rates of central air conditioning ventilation systems from 2016-2019 were 94.56%, 96.96%, 98.33% and 95.65%, respectively, and there was no statistically significant difference among them (P>0.05). The qualified rates of accumulated dust, total bacterium and fungus counts on the inner surface of the ducts were 100%, 98.34% and 98.67%, respectively. PM₁₀, total bacterium counts and fungus counts in the supplied air of the randomly selected 19 large public places were 100%, 63.15% and 78.94% respectively. The overall detection rate of Legionella pneumophila was 12.21%, and the detection rate of cooling water was larger than that of condensed water (P<0.05). Moreover, the detection rates of Legionella pneumophila in large shopping malls was 20.83%, which was higher than that of five-star hotels and leisure places (P>0.05). Conclusion The sanitary condition of the central air conditioning ventilation system in the public places of Nanshan district needed to be improved. Legionella pneumophila was still detected in some public places. Daily cleaning and disinfection management of central air condition systems should be strengthened.