Based on the soil respiration measurement methods, an introduction was made to the components, main characteristics, measurement principles, a typical measurement process and data output of the LI-8100 Automated Soil CO_2 Flux System. The LI-8100 has the flowing characteristics: high measuring precision; automated, continuous, unattended long-term measurements; fast, convenient, repeatable survey measurements; open path soil CO_2 flux measurements; designed to minimize perturbations within the chamber during measurements; measurements made at or near ambient CO_2 concentrations. The LI-8100 will play an important role in the researches on global carbon cycling.