In the current environmental context, it is now crucial to quantify precisely the environmental impacts for different ruminant livestock systems by using Life Cycle Assessment (LCA). The French Livestock Institute has launched a work program to determine the environmental assessment of beef cattle systems at the farm scale. A methodology based on life cycle assessment was built to assess GHG emissions. This methodology was applied to beef systems from the French Breeding Network database (calf-to-weanling system producing weaners and calf-to-beef system producing young bulls). French beef cattle systems produced from 12.8 to 15.3 kg CO2eq/kg of live weight. The calf-to-beef system producing weaners had the lower net carbon footprint (6.1 kg CO2eq/kg of live weight) considering carbon sequestration. At equivalent systems, an important difference was observed on the final impact between optimized and non optimized farms. These differences were due to herd management, cultural practices, feed and fertilizer strategies and highlight the relation between environmental issues and practices on farm, which propose some ways of mitigation adapted to the production systems.