In this article，we calculate seismic hazards from background seismicity by using a spatially smoothed seismicity model for Mongolia，and we obtain a peak ground acceleration （PGA）map for 10% probability of exceedance in 50 y.We propose two seismicity models to calculate seismic hazard maps for 10% probability of exceedance in 50 y.The results show that the seismic activity model and the seismic hazard results，both calculated by using the instrumental seismic catalog （M≥3.0），can reflect contemporary seismic activity levels and seismic hazard levels of the Mongolia area.In addition，the seismic activity model and the seismic hazard results，both of which are calculated by using historical earthquake data （M≥5.0），can quite well represent the seismic hazard level of moderate earthquakes in Mongolia.The two seismic hazard maps both show that the background seismic hazard level is 0.05 g in most areas of Mongolia and that the values of this parameter are high，at 0.1~0.15 g，in other areas，which indicates a background of high seismic hazards in Mongolia.Therefore，it is highly necessary to completely consider the impacts of background seismicity when implementing seismic hazard analysis and seismic hazard mapping for Mongolia. Moreover，we compare two seismicity models.The results also illustrate significant spatial differences between the seismicity models with different minimum complete magnitudes.Therefore，when adopting a spatially smoothed seismicity model to analyze seismic hazards for Mongolia，the weighted average of several different models should be considered to balance the impacts of earthquake occurrences and magnitudes.