Carbonyl sulfide (COS) is a long-living trace gas in the atmosphere, its' molecular structure, diurnal and seasonal dynamics of the tropospheric atmosphere mixing ratio are similar to carbon dioxide (CO₂). During plant photosynthesis and its' hydrolysis process, COS assimilation of stomata is closely related to CO₂, which is affected by the sharing diffusion pathway conductance and the enzymatic activities. Meanwhile, plant autotrophic respiration cannot release COS. In the latest studies, plant COS flux is used to indicate the ecosystem gross primary productivity (GPP) directly. In this study, we have reviewed the mechanism of association between plant COS flux and carbon fixation in photosynthesis, as well as the most recent research progresses of either eddy covariance COS flux observation, or the method which couples atmospheric COS monitor and ecosystem process model. And we have further dicussed the key ecological processes and parameters when use COS flux to indicate GPP. We have found these methods are confronted with the following bottlenecks:1) the physiological processes, scale effects, and decoupling effects can affect the leaf relative uptake rates (LRU) of COS and CO₂; 2) the observation and simulation methods need to be further integrated; 3) the density of global COS observation sites have limited method validation; 4) The sulfur cycle process have affected the accuracy of multi-regional simulation. The frontier areas of these methods breakthrough include:1) carry out COS flux observation in key areas and multi-biomes; 2) improve the coverage of atmospheric COS monitor by satellite column concentration; 3) improve the ecosystem process model by COS absorption mechanisms. The scientific issues this article focus on are:In the subtropical region, as well as some other regions in urgent need of atmospheric COS and COS flux observations, how about the accuracy and uncertainty of applicating as a direct proxy of GPP?