Abstract: Gas-solid two phase discrete random trajectory model is built up based on a series of relevant analyses, including those of the particles' physical features in and out of the nozzle, the particles' characteristics in shape and size, reciprocity between jet flow and particles etc. Numerical simulation are then performed. Results of calculation showed that the pulsate phenomenon in the gas-solid two phase jet flow can be effectively simulated with the random trajectory model. Results of calculation are consistent with that of the experiment. Conclusion drawn are that reciprocity between jet flow and the particles, can resist gas motion and transmit heat along the jet and will in the end influence the flow-field structure of the two phase jet flow.