Abstract: The straightening intermesh as the main straightening technical parameter， which decides the precision for straightening thinwalled tubes， is usually carried out based on the experiential data and chart by experience and experiments. Firstly a new simplified mechanical model for calculating the intermesh is presented， and the bendingmoment of the cross section is subsequently obtained in the elastic zone and also in the elasticplastic zone. Then the model of the straightening intermesh is presented by the integration of the bendingmoment equation. In order to certify the correctness， some dynamic simulations were done by LSDYNA， and the results indicate that the model is correct. An intermesh curve is plotted using the datum calculated with the model， by which the influence of the parameters can be analyzed qualitatively， thus the theoretical basis for adjusting the intermesh for the production can be provided.

Key words: thinwalled tube, straightening, intermesh, uniaxial stress, LSDYNA