A new process has been suggested for the esterification of oleic acid with methanol catalysed by a cation exchange resin, in which water is removed by simultaneous extraction with excess methanol as the extractant, and an algorithm for the simulation of countercurrent multistage extraction-coupled reaction processes has been proposed. The algorithm was applied to the new process and was proved to have good convergence. The calculated results showed that methyl oleate product with high yield and high purity could be obtained in the multistage countercurrent extraction-coupled esterification process. It was found that both yield and purity of methyl oleate product increase with the increase in the feed ratio of methanol/oleic acid as well as in the number of stages. A feed ratio more than six (in mole base) is required to obtain the purity and/or the yield higher than 95%. Purity of 99% and yield of 99% can be achieved in a four to nine stage process with a feed ratio of more than 8.5-16 when using 100% pure raw methanol.