The element carbons are almost completely from the burning of plants, they exist in many natural reservoirs, such as atmospheres, soils, sediments, rocks, waters and ices, with long-term stability and wide distribution, and they record abound of paleoenvironment informations. The carbon isotope of element carbon (δ13CEC) provides important evidence for the reconstruction of paleoenvironment. In this article we analyzed a great deal of scholars’ researches about using the δ13CEC proxy to study the paleoenvironment, and concluded that there were still some different views on the problem of whether this proxy can be used in recovering paleovegetation directly. Whether the carbon isotope changes during burning process is a very important problem to consider when we use δ13CEC to research the paleoenvironment. The scholars at home and abroad have done many researches on the burning experiments during the past twenty years, and their major conclusion was that the carbon isotope different between “before burning” and “after burning” (Δδ13C) for C3 plants was small, in±1‰; but Δδ13C rang for C4 plant was large, from 0‰ to -9‰. In addition, we discussed other possible factors that may impact δ13CEC, like exogenous input. We suggested that before using δ13CEC proxy to study the paleoenvironment, it’s necessary to do detail basic researches to study the relevance between the surface soil δ13CEC and the surface plants, and the exogenous input problem.