Boreal forests retain larger carbon reserves than other biomes. The boreal forests of China are in the Great Xing'an Mountains region, which contains approximately 24%-31% of the total forest carbon storage in China, and thus plays an important role in maintaining the national carbon balance. Timber harvest is a major anthropogenic disturbance in boreal forests, affecting forest structure and aboveground forest biomass over the long term. High-intensity harvest has resulted in simplification and homogenization of forest structure and composition in the past. Therefore, the Natural Forest Conservation Policy and the Commercial Harvest Exclusion Policy were successively implemented in 2000 and 2014, respectively, to balance ecological restoration and timber supply. The objective of this study was to investigate long-term effects of Commercial Harvest Exclusion on the structure and biomass of a boreal forest landscape in northeastern China. To do this, we simulated the effects of Natural Forest Conservation and Commercial Harvest Exclusion on forest structure and biomass using a spatially explicit forest landscape model (LANDIS PRO).We initialized the model using forest inventory data (second and third tier data from 2000) and conducted simulations for the Great Xing'an Mountains from 2000 to 2100. Our results suggested that 1) density and basal area between the initialized modeling results and forest inventory data in 2000 were consistent (P<0.01), suggesting that the initialized model results could represent the real forest landscape, and harvest results adequately represented real harvest events. 2) Larch and birch were now dominant, whereas a low proportion of aspen and spruce was present. Compared to the Natural Forest Conservation scenario, the Commercial Harvest Exclusion reduced the diversity of tree species by raising the proportion of the dominant species (larch and birch) and reducing the proportion of protected rare species (pine and spruce). There was a significant effect on forest composition in the medium and long-term periods. Overall, basal area was higher and density was lower under the Commercial Harvest Exclusion scenario than those under the Natural Forest Conservation scenario. 3) Commercial Harvest Exclusion strongly decreased tree abundance in the early stage and increased their abundance in the late, old-growth stage. 4) Compared to the Natural Forest Conservation scenario, the simulated biomass and rate of forest regeneration increased under the Commercial Harvest Exclusion scenario across all simulation periods. Commercial Harvest Exclusion helped to increase overall forest biomass, but reduced the biomass of pine and spruce, two rare and economically important species, suggesting that greater intensity of sylvicultural treatments are needed. These results could help to develop a forest management policy for the region.