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In order to analyze the temperature distribution of porthole die in extrusion process for automobile aluminum alloy, FEM was employed based on the principle of rigid plastic. The influences of extrusion speed and friction on temperature field in different directions (parallel and perpendicular to extrusion direction) were studied, and the feature points were selected in welding position to research its temperature distribution. The numerical results show that the difference between the maximum and the minimum temperature is from 7 to 8 ℃ in the X direction and from 9 to 10 ℃ in the Y direction respectively under an initial temperature of the billet 450 ℃, the friction factor 0.3, extrusion speed from 1 to 3 mm·s-1. Through the analysis on the temperature field，it is found that the temperature of the feature points near extrusion cylinder wall with good heat dissipation conditions declines to some extent. However, the temperature of some feature points in the internal declines a little, and there is different heat exchange between points and blank heat. Thus, the temperature declines slightly, and the abnormal rise happens in some points.
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