Open filed biomass burning is a major contributor to airborne particulate matter and reactive trace gases during the post-harvest season in the Northeastern China. Due to prevailing weather conditions and high emission density, this region is prone to the accumulation of air pollutants that often leads to severe haze events. In this study, we combined satellite and ground observations, and a regional air quality modeling system to quantify the con- tribution of open biomass burning to surface PM2.5 (particulate matter with diameter less than 2.5 mu m), concen- trations during a severe haze episode. During this period (November 1st - 4th 2015), the average PM2.5 concentrations in Heilong-jiang, Jilin, and Liaoning provinces reached 116.98 mu g/m(3), 98.60 mu g/m(3), and 70.17 mu g/m(3) respectively. Model simulations showed that open biomass burning contributed to 52.7% of PM2.5 concentrations over Northeast China. Using the differences in active fire spots as detected by the Visible Infrared Imaging Radiometer Suites (VIIRS) aboard the Suomi-NPP, we estimated that the burning ban enforced in 2018 have caused the PM2.5 concentrations to decrease from the 2015 level by 67.10%, 53.23%, and 10.06% in the Heilong-jiang, Jilin, and Liaoning provinces respectively. Over the region, the burning ban proved to be effective in reducing fire emissions and lowering region-wide PM2.5 concentration by 48.1% during the post-harvest season. (C) 2020 Elsevier B.V. All rights reserved.