An Unattended Detection method for monitoring the CO2 concentration in soil respiration is described. It is based on the gas pump and gas extraction with a dynamic air chamber assay, and the study of the relationship between data collected from on-line measurement of carbon dioxide and time, as well as the resistance to interfering. This method uses proposed utility line peak extraction method to extract the CO2 concentration in the soil respiration chamber, and sets up a mathematical model of soil CO2 concentration. The system equipment is independently developed and it is verified that the extraction method is feasible with the site automatically detection. This method which detects multiple signals at the same time and improves data reliability has a high reference value for the similar characteristics of data on-line extraction, comparing with the traditional CO2 concentrations of soil respiration detection methods.