OBJECTIVES:  To study the association between air pollution and low birth weights (LBW), stillbirth and premature birth, and estimate burden of pneumonia on children aged less than five in Mongolia. METHODS:  Data on total birth cases, LBW, premature infant, stillbirth, the morbidity and mortality from respiratory diseases among children under five, and air quality were collected from relevant institutions in Mongolia. Case-control study was applied to determine the relationship between air pollution and stillbirth. DALY was estimated considering influence of small particles on children with pneumonia RESULTS:  The level of SO and NO contained in air around Songinkhairkhan district, Ulaanbaatar city was up to 4 times higher compared to the standard. The proportion of women who delivered LBWs was relatively high in Bayangol and Chingeltei districts. Proportion of LBW babies was relatively high during winter season (p=0.022). Premature birth was associated with spring season (p=0.032). Probability of premature birth by 12.2 and 8.89 weeks had an association with increasing level of SOand PMin the air. Increased amount of SOby 10 units in the first, second and trimester was associated with the risk of stillbirth (OR=1.01 CI: 0.99-1.03). The presence of NOduring first trimester was associated with increased risk of stillbirth (OR=1.01 CI: 0.96-1.07). In addition, CO present in whole pregnancy is significantly associated with risk of stillbirth (OR=1.01 CI: 0.98-1.04). In 2014, 39% of children died from pneumonia were impacted by air pollution, and those children had 95,901 years of lost lives. By implementing rational actions against air pollution by 2024, children aged less than five years of lost lives from pneumonia influenced by polluted air would be 40424. CONCLUSIONS:  Increased air pollution causes reduction of birth weight by 138 grams, elevated levels of large particles and SO increase the risks of premature birth and stillbirth by twice. Implementation of rational actions against air pollution would decrease years of lost lives of children under five from pneumonia influenced by air pollution.