Vietnam's textile and garment industry has been developing strongly and plays an increasingly important role in economic growth of the country since recent years. However, in Vietnam, there are currently no specific and officially published statistics on the carbon footprint in the garment industry. Meanwhile, Vietnam currently has strategies and policies for sustainable economic development based on the approach towards a low-carbon economy and green growth. Aiming at greenhouse reduction, a carbon footprint calculation method is presented. In carbon footprint calculations, allocation methodology is among the most significant. In this paper, based on characteristics of textile and apparel industry, process-level allocation methodology in textile and apparel industry was put forward with case study in 2020 for sewing processes for businesses of Vietnam National Textile and Garment Group (VINATEX). the amount of carbon that is emitted during the production process at the garment factory including 14 sewing lines at Phong Phu JSC and 3 sewing lines at Nha Be Garment Joint Stock Company. The results show that, on average, in 8 months of 2020, Phong Phu Garment Joint Stock Company discharged 334304.5548 Kg CO2e mean while Nha Be Garment Joint Stock Company emitted 118026,998 Kg CO2e.This case study had proposes options to reduce greenhouse gas (GHG) emissions, including: Designing appropriate factories, distributing and minimizing lighting equipment to minimize GHG emissions. Upgrading old production equipment with new, advanced and more energy-efficient ones is aimed at reducing emissions as well as improving product productivity.