Abstract: Objectives To explore the relationship between fine particle matters (PM_2.5)in the ambient air and the mortality of respiratory diseases in Fengtai district of Beijing in 2013.Methods Describing the pollution of PM_2.5, the mortality of respiratory diseases and meteorological factors, and analyzing their relevance in Fengtai district of Beijing in 2013. Establishing a distributed lag nonlinear model (DNLM)to explore the effect of PM_2.5 on the mortality of respiratory diseases by controlling long-term trends and meteorological factors, and to analyze the association between PM_2.5 pollution and the mortality of respiratory diseases.Results The average concentration of PM_2.5 was 100.92 μg/m³, and there were 764 people died of respiratory diseases in Fengtai district of Beijing in 2013. The concentration of PM_2.5 was positively correlated with daily average relative humidity, the total mortality of respiratory diseases and the mortality of respiratory diseases in the female (P<0.05). There was no correlation between the concentration of PM_2.5 with daily average temperature, daily average air pressure and the mortality of respiratory diseases in the male. The rising of PM_2.5 concentration on each 10 μg/m³, the relative risk (RR)for the death from respiratory diseases was 1.0252 (95%CI: 1.0113-1.0393)in the same day.Conclusions The average concentration of PM_2.5 in Fengtai district of Beijing in 2013 was 100.92 μg/m³, which was 34.56% higher than that of the second level of national standard limits. The number of death from respiratory diseases was increased with the increase of PM_2.5 concentration in Fengtai district of Beijing in 2013.