Biochar has a strong ability to sorb various pollutants due to its unique surface properties, morphological characteristics and abundant, discretely-distributed pores, implying a great potential for use in soil pollution control and remediation. Following field application of biochar to soil, various ageing processes may occur due to the decomposition and leaching of biochar’s labile components and the interactions between biochar, soil and microbes, leading to significant changes in biochar’s chemical and physical properties over time. These mixed, complicated changes can be classified into: chemical changes (e.g., loss of inorganic elements, changes of surface functional groups, partial mineralization of unstable components) and physical changes (e.g., changes of pore system resulting from surface coating by soil-origin organic matter and minerals). Biochar’s ageing may lead to changes in characteristics of sorption and desorption of organic pollutant in soil, which are highly dependent on properties of soil, biochar and organic pollutant. In this paper, the mechanisms and influential factors of biochar ageing in agricultural soil as well as its effects on the sorption and desorption of organic pollutants are reviewed, and the focuses of future study are also proposed.