The paper industry is an essential but energyintensive economic sector. This study aims to propose an appropriate inventory method to first determine the GHG emission factor in the life cycle of paper products of Vietnam. The approach overcomes the limitations of the ISO 14067 method by including the environmental burdens from the paper mill’s processes. In 2018, the amount of GHG emitted from cradle to gate when producing a ton of carton box, writing paper, and tissue products (EFCO2eq) was 1,366 kg CO2eq, 1,224 kg CO2eq, and 751 kg CO2eq, respectively. High energy intensity is identified as the main reason that causes high life cycle analysis (LCA) GHG emission factors and virgin paper-based products often emit higher LCA GHG amounts than recycled paper-based products. To reduce the emission, the Vietnamese paper mills should increase the use of recycled paper and replace fossil fuels with environmentally friendly energy resources.