Abstract: To explore the fluid temperature change law of twin screw extruder, a fluid-temperature coupling model of non-isothermal Newton fluid was constructed based on the rheology theory. The temperature distribution discipline of fluid in the extruder was simulated with the initial temperature T at 423, 433 and 443 K, respectively. Results showed that the fluid temperature increased by 5 K, high temperature circle in meshing district expanded quickly. The fluid temperature was changed uniformly at the beginning of the screw extruder，then the fluid flow exited out of the extruder isothermally. Several optimum product conditions of twin screw extruder were verified with food expanding experiments. This research could provide references for twin screw extruder processing.