Abstract: A stochastic model of the residence time distribution was established on the basis of a continuoustime Markov chain and some knowledge of matrix. According to the measurement of flow field for the opposed tetraburner gasifier, the gasifier was divided into several regions and the Markov chain states transfer diagram was formed. It is found that the calculated results can give a reasonable fit for the experimental data when the reflux ratio of jet reflux region and impinging stream reflux region is 1, and the tube stream region can be regarded as PFR, the other regions as CSTR. Based on the established model, the residence time distribution of cold model gasifier for different conditions is predicted. It can be concluded that the mean residence time is reduced and the variance is increased with the increase of flow rate. The mean residence time is increased and the variance is reduced with the increase of gasifier height. The prediction of residence time distribution for an industrial opposed tetraburner gasifier shows that the flow pattern of industrial gasifier is closed to CSTR, which is beneficial to the gasification reaction.