Abstract: Soil CO₂ concentration is the consequences of biological activities in above and belowground, and its fluctuation may significantly affect the future atmospheric CO₂ concentration and the projected climate change. This paper reviewed the methodologies for measuring the soil CO₂ concentration in situ as well as their advantages and disadvantages, analyzed the variation patterns and controlling factors of soil CO₂ concentration across the temporal (diurnal, several days, seasonal and interannual) and spatial (soil profile, site and landscape) scales, introduced the primary empirical and mechanical models for estimating and predicting soil CO₂ concentration, and summarized the applications and constraints of soil CO₂ concentration gradient in determining soil respiration. Four research priorities were proposed, i.e., to develop new techniques for collecting and determining the soil CO₂ in severe soil conditions (e.g.,flooding, lithoso and others), to approach the responses of soil CO₂ concentration to weather change and related regulation mechanisms, to strengthen the researches on the spatial heterogeneity of soil CO₂ concentration, and to expand the applications of soil CO₂ concentration gradient in the measurement of tropicalsubtropical soil respiration.