The numerical simulation for the microstructure of U-2Nb alloy tube\|like part with 107 mm/77 mm×80 mm under cooling rate of 50 ℃/min was conducted by CA\|FE module（cellular automaton-finite element） in Procast and Calcosoft-3D software. The results showed that the sequence of casting grain size varied from the inner to the outer layers in the section of the casting part at the same level in height as follows : grain size in the inner position<grain size in the outer position<grain size in the middle position. The grain size gradually reduced from the top to the bottom of the part. Although the measured value of grain size in the middle position at different level in height of U-2Nb alloy parts with optical metallographic method was approximately a half of calculated values

the change in trend of the both grain sizes is the same. The simulated results reached to the qualitative or semi-quantitative level.