Ground鄄level ozone (O 3) is a major pollutant with adverse effects on plant growth and yield. The impact on plants is generally studied by controlling the O 3 concentration using the open top chamber (OTC) method. The effects of O 3 on ecosystems are studied by combining assessment models and indices, calculated using O 3 concentration or flux measurements over the vegetation. As these effects are related to the level of O 3 entering into the plant忆s gas exchange, compared with concentration鄄based indices, the O 3 stomatal flux鄄based indices are considered the better standards for evaluating the influence of O 3 on ecosystems. In China, the rapid industrialization and urbanization has resulted in elevated O 3 concentration which is threatening crop production and yields. Studies are required to elucidate the O 3 risk鄄assessment indices, including consideration for the status of the plant. In this paper, we analyze the advantages and disadvantages of two kinds of assessment indices. We then introduce several O 3 flux observation and stomatal uptake estimation methods at ecosystem scale. We also review the progress in O 3 flux observations, stomatal uptake estimations and risk assessment across different ecosystems. Additionally, we present case studies and the future prospects of O 3 research in China. Concentration鄄 based indices are easily observed and calculated, but these types of indices are often lacking sufficient, robust experimental design and data. In contrast, O 3 flux鄄based indices are difficult to obtain, although they incorporate the status of the ecosystem. The method used for measuring O 3 flux is mainly the eddy covariance technique, generally seen as the best modern technique. However, this method is inferior compared with CO 2 / H 2 O flux measurements. The lack of a fast鄄response